Was the secession of the Confederate states illegal?

The US Constitution applies only to the territory within the US. If a state withdraws from the union it no longer is obligated to comply with the demands of said constitution. "Legality" is in the eye of the beholder or rather the entity that prescribed the law. Those laws no longer apply to a withdrawn state any more than they do to an African nation.

No its not legal they did not gain permission to secede and so thus they broke the law if they were to secede they would have had to go through several different courts and several different government actions would have to happen. They illegally withdrew from the u.s. and they had to pay the consequence for there actions.

The Articles of Confederation that the original colonies/states signed meant they joined the federal government in "perpetual union". But they different states would always threaten to leave the union if they did not get their way- meaning each state was it's own basic nation, just in an agreement to help one another more or less. However, seeing this problem keep coming up, they then decided to write the US Constitution- which in effect threw the Articles away and bound the states together under one goverment with the states holding certain rights of the own, but limiting their ability to operate as a free county on their own. Now in the event of armed rebellion but the PEOPLE of the state, not the governments, as well as the PEOPLE voting to leave the Union, not just the government making the choice for them- which is very much what happened in the Civil War when the state broke away, they did not do so at the full will of the people, but as the governmnet reprsentaives, who stood to gain power by breaking away, and not the best interest of the people. So yes, but doing the break away in that form, the South DID break away illegally, where as if put to a vote (just like Scotland did this week)where the people really effected go to choose, then that would ahve been legal had they left the union and then the Northern attacks would have been the illegal act. But after Reconstruction and the states rejoining the nation, State Rights were vastly limited by readmission and even in the states that did not leave, that is one fall out from the Civil War, that it allowed the Constitution to be changed without really anyone to stop them.

Question:
Was the succession of the confederate states illegal?

If it wasn't illegal per se then, is it now? Did the post-war Union act to make it more difficult for states to secede in the future?

This question is not the same as, but is related to and informed by American Presidents on secession legality

This debate is older than our constitution(ratified 21 June 1788). The modern vestiges of this argument occur every four years during elections with the call for states rights and trepidation some feel of the Federal Government usurping these rights. It reared its head in the 1960's over integration, and in the 21st century over healthcare. It was first debated 1786, when a farmer and former Colonial Captain named Daniel Shays lead 4000 like minded farmers and would be revolutionists in an attack on the federal armory in Springfield Massachusetts. The differences between the founding fathers in Union Troops being raised and used to put down this rebellion gave rise and urgency to the ratification of the US Constitution.

On one side of the argument you have Thomas Jefferson who both opposed the ratification of the Constitution and believed it was every states right to leave the Union which it had freely joined.

Thomas Jefferson(March 4, 1801) in his First Inaugural Address said “If there be any among us who would wish to dissolve this Union, or to change its republican form, let them stand undisturbed as monuments of the safety with which error of opinion may be tolerated where reason is left to combat it.”

...

I trust not. I believe this, on the contrary, the strongest Government on earth. I believe it the only one where every man, at the call of the law, would fly to the standard of the law, and would meet invasions of the public order as his own personal concern. Sometimes it is said that man can not be trusted with the government of himself. Can he, then, be trusted with the government of others? Or have we found angels in the forms of kings to govern him? Let history answer this question.

James Madison (1788) At the Constitutional Convention, a proposal was made and rejected to allow the Federal Government to suppress a seceding state

“A Union of the States containing such an ingredient seemed to provide for its own destruction. The use of force against a State, would look more like a declaration of war, than an infliction of punishment, and would probably be considered by the party attacked as a dissolution of all previous compacts by which it might be bound.”

On the other side of the Argument you have George Washington

George Washington 1783 It is indispensable to the happiness of the individual states, that there should be lodged somewhere, a supreme power to regulate and govern the general concerns of the…republic, without which the Union cannot be of long duration. That there must be a faithful and pointed compliance on the part of every state, with the…proposals and demands of Congress, or the most fatal consequences will ensue; that whatever measures have a tendency to dissolve the Union, or contribute to violate or lessen the sovereign authority, ought to be considered as hostile to the liberty and independency of America, and the authors of them treated accordingly….[W]ithout an entire conformity to the spirit of the Union, we cannot exist as an independent power.

The Core Secessionist Augment: In the Constitution succession is not outlawed, and thus by the tenth Amendment, “The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people”; secessionists have a rational argument to be made.

From a historical perspective however, warnings come down to us in the federalists papers that dissolution of the Union is among the worst things the founding fathers could envision. Hamilton, Madison and Jay all agree that if such a thing were to happen it would condemn the two parties to fight 1000 years of wars along competing religious, economic, and social values; just as Europe had done in the centuries before.

Thus succession for unionists transcends hypothetical discussions and the logic of default arguments. They are transformational disputes at the root bundle of the republic.
Every succession attempt, whether Daniel Shay in 1786, South Carolina in 1832, or the entire South in 1861; has been meet not by legal petitions or counter arguments but by force of arms.

Sources:
Shay's Rebellion
Thomas Jefferson on Shay's Rebellion
American Presidents and the legality of succession

The 10th Amendment:

The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.

The power to secede was not granted to the Federal government. Therefore, it is reserved for the States.

Well it seems that the power to be the United States is delegated to the United States!

However, the case of succession was tried, trial by combat (honorable medieval method methinks), and the case was decided by the barrels of guns in the negative.

It is simple, secession was and is legal. Look to the ratification documents from Rhode Island, New York and Virginia, three of the last four to ratify the Constitution. They state specifically, that the State can reassume the powers delegated through the ratified Constitution by the State in cases where they feel they are being injured or abused. This is a quote from the Virginia ratification document for reference.

DO in the name and in behalf of the people of Virginia, declare and make known that the powers granted under the Constitution, being derived from the people of the United States may be resumed by them whensoever the same shall be perverted to their injury or oppression, and that every power not granted thereby remains with them and at their will:. . . Ratification of the Constitution by the State of Virginia

Of course secession is legal.

The only way that states join the United States is via a ratification of the Constitution in which they VOLUNTARILY agree to join.

Therefore, if they later reject that Constitution ("un-ratify" it, if you will) then they are no longer bound by its laws.

Secession is simply that process of rejecting the original ratification.

I had originally answered yes; then I discovered the force bill. Section 5 of the force bill permits the President to use whatever force is necessary to preserve the Union. The US Congress had considered seccession, and explicitly authorized the preservation of the Union by military force.

UPDATE: @Garrett Albright asks a pertinent question. I grant you that my argument is indirect, but if the United States authorized military force to preserve the Union, then implicitly any effort to sever the Union is illegal.

The secession of the southern states was a violation of Section 10 of the US Constitution, to which all of those states had agreed. That part of the Constitution reads:

No State shall enter into any Treaty, Alliance, or Confederation; ..

By creating the Confederacy, they obviously were breaking this clause of the constitution to which they had previously agreed.

Of course, at the sovereign level there is no such thing as "illegal". Laws are for consenting communities that agree to live together under a fixed set of rules. When the communities fight, those laws are no longer valid. From the answers above you can see that the US Congress and Supreme Court, ex post facto, passed a bunch of "laws" that it was "illegal" for a state to succede, but at the end of the day, there are no laws, just force.

For example, lets say Congress passes a law that makes it "illegal" for anyone in Somalia to mine tin. Does that mean it is illegal for Somalis to mine tin. I suppose so, in the eyes of Congress, but probably not in the eyes of the Somalis.

For a law to have just force, the court must have jurisdiction. When a group seccedes, they may argue there is no longer any jurisdiction over them. For example, William Wallace, after being captured, was charged with treason, but he argued, correctly, that there was no treason because he was not a subject of the English king, Edward. That didn't stop Edward from killing him though.

JimZipCode wrote a long and passionate answer which tries to debunk many of the other answers here and claim that the law was settled before the Confederate states seceded. He brings up some interesting points that should be debated.

However, he also clearly goes too far. His choice of quotations is selective: I could just as easily come up with dozens of quotations from learned authorities from both the North and South before the Civil War that argue both sides of whether secession was legal or not.

The real meat of his answer, though, concerns whether stare decisis would already be in effect due to previous court rulings, thus making Texas v. White a restatement of previously settled law, rather than a novel interpretation.

He cites three previous Supreme Court cases as evidence. However, if there were indeed clear precedent, that matter should be made clear in the rulings of Texas v. White. When we examine that ruling thoroughly, there is no mention of any of the precedents cited in JimZipCode's answer, nor is there any clear reference to his notion of "Compact Theory."

To the contrary, the majority ruling written by the Chief Justice Salmon Chase (a former member of Lincoln's cabinet) clearly implies that there had been previous legal disagreement about this question:

We are very sensible of the magnitude and importance of this question, of the interest it excites, and of the difficulty, not to say impossibility, of so disposing of it as to satisfy the conflicting judgments of men equally enlightened, equally upright, and equally patriotic. But we meet it in the case, and we must determine it in the exercise of our best judgment, under the guidance of the Constitution alone.

Note that he clearly states that "we must determine it" according to "our best judgment," not that it was a matter of previously determined or settled law.

Furthermore, when we examine the dissents in the 5-3 ruling, they actually cite another case where John Marshall speaks directly to the definition of a state. Justice Grier writes:

I do not think it necessary to notice any of the very astute arguments which have been advanced by the learned counsel in this case to find the definition of a State, when we have the subject treated in a clear and common sense manner by Chief Justice Marshall, in the case of Hepburn & Dundass v. Ellxey. As the case is short, I hope to be excused for a full report of it as stated and decided by the court. He says:

The question is whether the plaintiffs, as residents of the District
of Columbia, can maintain an action in the Circuit Court of the United
States for the District of Virginia. This depends on the act of
Congress describing the jurisdiction of that court. The act gives
jurisdiction to the Circuit Courts in cases between a citizen of the
State in which the suit is brought and a citizen of another State. To
support the jurisdiction in this case, it must appear that Columbia is
a State. On the part of the plaintiff, it has been urged that Columbia
is a distinct political society, and is therefore a "State" according
to the definition of writers on general law. This is true; but,
as the act of Congress obviously uses the word "State" in reference to
that term as used in the Constitution, it becomes necessary to inquire
whether Columbia is a State in the sense of that instrument. The
result of that examination is a conviction that the members of the
American Confederacy only are the States contemplated in the
Constitution. The House of Representatives is to be composed of
members chosen by the people of the several States, and each State
shall have at least one representative. "The Senate of the United
States shall be composed of two senators from each State." Each State
shall appoint, for the election of the executive, a number of electors
equal to its whole number of senators and representatives. These
clauses show that the word "State" is used in the Constitution as
designating a member of the Union, and excludes from the term the
signification attached to it by writers on the law of nations.

Now we have here a clear and well defined test by which we may arrive at a conclusion with regard to the questions of fact now to be decided.

Grier goes on to apply Justice Marshall's definition of "state" to the situation in Texas. From this, he concludes that Texas is not (and was not, during the Civil War) a "state," according to laws in force by Congress. He concludes:

I can only submit to the fact as decided by the political position of the government, and I am not disposed to join in any essay to prove Texas to be a State of the Union when Congress have decided that she is not. It is a question of fact, I repeat, and of fact only. Politically, Texas is not a State in this Union. Whether rightfully out of it or not is a question not before the court.

The other two dissenting justices (Noah Swayne and Samuel Miller) concur with Grier on this interpretation that Texas is NOT a state according to current law (though they agree with Chase regarding other issues in the case).

(By the way, Grier's opinion here was also implicitly endorsed by Congress and actually by many historical sources today which cite the dates of apparent "readmission" to the Union as happening between 1868 and 1870. These were the dates that representatives from these states were readmitted to Congress, and there were generally conditions placed on those states before the representatives were allowed to rejoin Congress. If secession were truly "unconstitutional" according to Chase's argument which effectively said secession never happened, then Congress was acting unconstitutionally by refusing to seat representatives -- as required by the Constitution -- until they capitulated. It also implies that the various plans to set conditions on "readmission to the Union" were legally nonsensical. The more consistent interpretation is that the states actually had seceded, at least according to pragmatic politics as Grier argues, as well as according to Constitutional requirements stated for what current states were entitled to. This doesn't argue whether secession was "legal" or "illegal," only that it had in fact happened, which implies that it wasn't thought unconstitutional on its face.)

TO SUMMARIZE: The cases cited in JimZipCode's answer were not actually mentioned or even hinted at in Texas v. White, so they clearly were not considered as settled precedent to which stare decisis must apply. The majority opinion itself implies that it is making a determination according to present judgment, and 3 of the 8 justices rejected that interpretation, instead citing a different precedent of John Marshall's, as well as current law in Congress, to claim that Texas was not a state.

Obviously dissents are not law. But here they are strong evidence that the matter wasn't even clearly settled among those on the Court in 1869, and the dissent actually lines up well with how the Executive and Legislative branches had been treating the states (i.e., as though they had actually seceded). And the majority opinion -- written by a member of Lincoln's cabinet who presumably had been aware of earlier legality of secession debates -- acknowledges that it's still an openly debated issue among many learned people which must be settled in this ruling.

Solely on the basis of the ruling in Texas v. White, a reasonable interpretation would conclude that the matter had not been settled law previously. This is not unusual in Supreme Court rulings: novel Constitutional interpretations are often applied retroactively to earlier circumstances that led to a case. In fact, it's difficult to figure out how the Court could function otherwise unless all Constitutional interpretation had been previously settled once and for all time. This does not imply the secession was "legal" in 1861, only that it was not clearly settled law at that time.

In 2 court rulings this century the pre-civil war secession situation was described as either unresolved or unsettled, not illegal or unconstitutional.

In 2004 the SCOTUS observed that inclusion of the word “indivisible” in the Pledge of Allegiance was significant because “the question whether a State could secede from the Union had been intensely debated and was unresolved prior to the Civil War.” (Elk Grove Unified Sch. Dist. v. Newdow, 542 U.S. 1, 6 n. 1, 124 S.Ct. 2301, 159 L.Ed.2d 98 (2004). )

In KOHLHAAS v. STATE OFFICE OF LIEUTENANT GOVERNOR http://ak.findacase.com/research/wfrmDocViewer.aspx/xq/fac.20100115_0000025.AK.htm/qx, The Alaska Supreme Court ruled in a case involving the right to secede, that “While a state's ability to secede was an unsettled question before the end of the Civil War, subsequent United States Supreme Court opinions have concluded that secession is clearly unconstitutional, “

Also Justice Scalia in a letter http://www.newyorkpersonalinjuryattorneyblog.com/uploaded_images/Scalia-Turkewitz-Letter-763168.jpg observed "If there was any constitutional issue resolved by the Civil War, it is that there is no right to secede."

This seems to indicate that the interpretation of Texas v. White as addressing antebellum law may not be correct.

We can go into these long winded discussions on Supreme Court decisions and the law about secession. A document that is more important than the Constitution is being overlooked. The Declaration of Independence. Does this not give a state the right to break away from a government that has become destructive to the people. What did we do when be declared independence from England. Did the Southern states in succeeding declare independence from the United States. Here in the south you can see on some grave stones of Soldiers inscriptions stating they were fighting for Southern Independence. To say that the southern states, or any other state for that matter would have the right to declare independence. If secession is illegal then we committed an illegal act when we broke away from England. Also these decisions were decided after the war. What other way would they have went. I guess at the end of the day right and wrong are decided at the end of a barrel and bayonet.

My cynical reasoning is that it's illegal because the pro-union side won. Laws are often changed and legal justification can be found for most things after or before the fact. Legal experts are rarely 100% in agreement in everything (even now, supreme court judgements have various opinions).

Sometimes people ask these questions because they equate "legal" with "moral" and "illegal" with "immoral". Sometimes people will hunt around for legal justification for/against an act to try to show how it was moral/immoral.

Yes, the secession of the Confederate states was illegal.

It's important to understand that secession was not strictly, or merely, a “legalistic” matter. Secession was a hotly contested political issue that divided the electorate. It could not be settled by a judge. Any ruling in one direction or the other would be rejected by half of the population. See the last section here, esp the concluding two paragraphs, for a fuller discussion of this.

However, to the extent that secession was a LEGAL question, the “legalistic” aspect is very straightforward.

This answer is in three main sections:

1. The law of the land.
2. The arguments in support of the legality of secession.
3. Why those arguments fail.

Then there are two follow-up sections, on historiography and later legal commentators.

The Law of the Land

Unilateral secession has been illegal since the Articles of Confederation. No one ever mentions this, but the full title of that document was the "Articles of Confederation and Perpetual Union Between the States of [list]". (Emphasis added, obviously.) Article 13 laid out a possible mechanism for secession. It said:

"And the Articles of this Confederation shall be inviolably observed by every State, and the union shall be perpetual; nor shall any alteration at any time hereafter be made in any of them, unless such alteration be agreed to in a congress of the united states, and be afterwards confirmed by the legislatures of every state."

That language is awkward for modern ears to parse. I bolded the word "them" above. If "them" refers to the Articles, then this is a sentence about amending the Articles. But if "them" refers to the States, then this could be construed as a sentence about changing the composition of the States or changing the membership of the Union. So here is a potential legal way out of the Union: propose it in Congress, win passage there, and then get it ratified by every state. We might call that a "consensual", cooperative, amicable secession. But there's no support in the Articles for unilateral secession, where a state just decides on its own to leave.

The Articles created a much weaker national government, than the Constitution did. It follows that the stronger and "more perfect Union" created by the Consitution is, if possible, even more perpetual than the Perpetual Union created by the Ariticles. Certainly not conditional, or "less perpetual". That's the exact reasoning used by the Supreme Court in Texas v White. The Constitution says it is the supreme law of the land: there's no room for a state government to suspend or nullify it.

Here's the relevant section from the 1869 Texas v White ruling, which defines the current law of the land:

The Union of the States never was a purely artificial and arbitrary relation. It began among the Colonies, and grew out of common origin, mutual sympathies, kindred principles, similar interests, and geographical relations. It was confirmed and strengthened by the necessities of war, and received definite form and character and sanction from the Articles of Confederation. By these, the Union was solemnly declared to "be perpetual." And when these Articles were found to be inadequate to the exigencies of the country, the Constitution was ordained "to form a more perfect Union." It is difficult to convey the idea of indissoluble unity more clearly than by these words. What can be indissoluble if a perpetual Union, made more perfect, is not?

...

When, therefore, Texas became one of the United States, she entered into an indissoluble relation. All the obligations of perpetual union, and all the guaranties of republican government in the Union, attached at once to the State. The act which consummated her admission into the Union was something more than a compact; it was the incorporation of a new member into the political body. And it was final. The union between Texas and the other States was as complete, as perpetual, and as indissoluble as the union between the original States. There was no place for reconsideration or revocation, except through revolution or through consent of the States.

Considered therefore as transactions under the Constitution, the ordinance of secession, adopted by the convention and ratified by a majority of the citizens of Texas, and all the acts of her legislature intended to give effect to that ordinance, were absolutely null. They were utterly without operation in law.

One might wonder: was the 1869 ruling consistent with what the Founders had to say?

The debates at the Constitutional Convention don't have much to say about secession – possibly because the issue was already settled by the "perpetual" nature of the existing Union. There is a letter from Madison to Hamilton on the topic, from the Ratification era. Madison says:

"My opinion is that a reservation of a right to withdraw if amendments be not decided on under the form of the Constitution within a certain time, is a conditional ratification, that it does not make N. York a member of the New Union, and consequently that she could not be received on that plan. Compacts must be reciprocal, this principle would not in such a case be preserved. The Constitution requires an adoption in toto, and for ever. It has been so adopted by the other States." (Letter to Hamilton, July 1788)

The money soundbite is right there, the last 2 sentences.

Madison had more to say on secession much later in his life, when he was in his 80s, in letters to Trist (1830), and again to Trist (1832), and to Rives (1833), and to Daniel Webster (1833). I'm not bringing any of those quotes inline, as the letters don't date from the Ratification era; but they are from the Father of the Constitution, so they are worth looking at. Madison was of course a Virginian and a slaveowner.

Weak old Buchanan (of all people!) also made a Ratification-argument. In Buchanan's 4th annual message, just two weeks before South Carolina seceded, he said:

In order to justify secession as a constitutional remedy, it must be on the principle that the Federal Government is a mere voluntary association of States, to be dissolved at pleasure by any one of the contracting parties. If this be so, the Confederacy is a rope of sand, to be penetrated and dissolved by the first adverse wave of public opinion in any of the States. In this manner our thirty-three States may resolve themselves into as many petty, jarring, and hostile republics, each one retiring from the Union without responsibility whenever any sudden excitement might impel them to such a course. By this process a Union might be entirely broken into fragments in a few weeks which cost our forefathers many years of toil, privation, and blood to establish.

Such a principle is wholly inconsistent with the history as well as the character of the Federal Constitution.

Two notes on the language here:

1. The "rope of sand" metaphor that Buchanan uses above, is not casual. It's a deliberate reference to a famous quote from George Washington. You can find the original in Washington's letter to Knox of February 1785.

2. That word "Confederacy" in the quote is confusing. The actual Confederate States of America did not exist when Buchanan made his address. I think he is using the word in the general sense of "league or alliance" – basically another way to refer to the Union – or else to the govt established by the Articles of Confederation.

Buchanan also pointed out some pretty strong negative evidence: in the long fight for Constitutional ratification, no one ever tried to persuade reluctant states by arguing that:

"the moment that any state felt herself aggrieved she might secede from the Union. ... What a crushing argument would this have proved against those who dreaded that the rights of the States would be endangered by the Constitution!"

The absence of counter-evidence is not the same thing as positive evidence; but Buchanan actually raises a strong point. Constitutional ratification was protracted and difficult, with extensive discussion by the leading political minds of the day. They didn't just FORGET to mention a potential right to withdraw. It would have been exactly on-point for the issue they were arguing about, that the national government might be too strong & too centralized. But they didn't mention it; I think because the "perpetual union" had already been established a decade earlier.

Robert E Lee himself agreed with Buchanan's view. In a letter to his eldest son in January 1861, he wrote:

Secession is nothing but revolution. The framers of our Constitution never exhausted so much labor, wisdom, and forbearance in its formation, and surrounded it with so many guards and securities, if it was intended to be broken by every member of the Confederacy at will. It was intended for “perpetual union,” so expressed in the preamble, and for the establishment of a government, not a compact, which can only be dissolved by revolution, or the consent of all the people in convention assembled. It is idle to talk of secession. Anarchy would have been established, and not a government, by Washington, Hamilton, Jefferson, Madison, and the other patriots of the Revolution.

(Note that Lee uses the word "Confederacy" here the same way Buchanan did. The actual CSA still did not exist quite yet; it would be formed a couple weeks later.)

Lee's assessment matches that of his fellow Virginian, Madison. And the way he calls out the "perpetual union" language precisely foreshadows the Supreme Court ruling in Texas v White, written 8 years later.

The argument in support of secession

The basic argument is that the states agreed to enter into the US Constitution, like a contract, so they could decide to leave (terminate). But by itself that argument is severely flawed. Either party may opt NOT TO ENTER a contract; entering into a contract is voluntary by definition. But once a contract is entered into, it takes BOTH parties to dissolve it. One party can't dissolve a contract unilaterally.

To support unilateral secession, supporters invoke what is called "Compact Theory". Compact Theory is the idea that the United States is not a national government, but instead a compact between independent sovereign states. Somewhat like a League of Nations. Nations can unilaterally rescind treaties; so, under Compact Theory, could the states unilaterally rescind their membership in the US. Like France leaving NATO, or Australia pulling out of the UN.

You can see Lee referencing the theory in his letter to his son (above), when he uses the word "compact". Buchanan references it too, when he mentions "the principle that the Federal Government is a mere voluntary association of States, to be dissolved at pleasure by any one of the contracting parties." Compact Theory had a long and respectable pedigree in American politics; it was no fringe theory. Jefferson articulated it quite clearly in his 1798 draft of the Kentucky Resolutions.

This is really the entire argument. The states are not bound by anything like contract law. The states are sovereign, they entered into a compact, and they can withdraw from it at will.

Why the argument fails

Compact Theory had already been rejected by the Supreme Court in 1816, 44 full years before South Carolina seceded. The case was Martin v. Hunter's Lessee (1816). By the way, 4 of the 6 Justices who concurred in that ruling were Southern. (There was no dissent; Marshall recused for some reason.) One of them was George Washington's nephew. The ruling was that the Constitution was not an agreement between the states at all; rather, as the preamble says, it was ordained and established directly by the people. Justice Story wrote as part of the majority:

“The Constitution was for a new Government, organized with new substantive powers, and not a mere supplementary charter to a Government already existing. The Confederation was a compact between States, and its structure and powers were wholly unlike those of the National Government. The Constitution was an act of the people of the United States to supersede the Confederation...”

The status of Compact Theory was reiterated in McCulloch v. Maryland (1819); still 41 years before secession. 5 of the 7 sitting Justices in that case were Southern (still including the nephew); and the decision was unanimous. McCulloch extended Martin, with Marshall writing that "the constitution and the laws made in pursuance thereof are supreme ... they are binding on the states and cannot be controlled by them." This directly rejects Compact Theory, which would hold that the federal government is a creation of the states, where the states maintain superiority.

Both cases draw a distinction between the Articles of Confederation and the Constitution. In Martin the Court says that the Articles were a "Compact", but the new government is not. In McCulloch the Court says that there is no phrase in the Constitution, unlike the Articles, that "excludes incidental or implied powers". (Meaning that under the Constitution, the Fed govt has more power than what is explicitly mentioned in the document: it also has incidental or implied powers. The Fed govt did not have those under the old Articles.)

You can actually go back to Chisholm v. Georgia (1793) to see compact theory get its first beating from the Court. This was the original Court appointed by George Washington. The ruling there was that the People directly established "a Constitution by which it was their will that the State governments should be bound." Supreme or sovereign power was retained by citizens themselves, not by the "artificial person" of the State of Georgia. 1793! The 11th amendment undid part of Chisholm, making it impossible for citizens to sue other states in federal court; but it conferred Sovereign Immunity, not Sovereignty. No support for Compact Theory.

It's very straightforward. By 1820, Southern majorities of the Supreme Court had already rejected the only argument in support of the legality of secession, THREE TIMES. That's well before secession, and Texas v White.

That's just the actual opinions of the court. The standard work on Constitutional law in the 1800s was Justice Joseph Story's Commentaries on the Constitution of the United States (1833). Called "a cornerstone of early American jurisprudence" and still referred-to. Story doesn't mince words when it comes to Compact Theory:

In what light, then, is the constitution of the United States to be regarded? Is it a mere compact, treaty, or confederation of the states composing the Union... ? There is nowhere found upon the face of the constitution any clause, intimating it to be a compact, or in anywise providing for its interpretation, as such. On the contrary, the preamble emphatically speaks of it, as a solemn ordinance and establishment of government. The language is, 'We, the people of the United States, do ordain and establish this constitution for the United States of America.' The people do ordain and establish, not contract and stipulate with each other. The people of the United States, not the distinct people of a particular state with the people of the other states. The people ordain and establish a constitution,' not a confederation.' . . . Nor should it be omitted, that in the most elaborate expositions of the constitution by its friends, its character, as a permanent form of government, as a fundamental law, as a supreme rule, which no state was at liberty to disregard, suspend, or annul, was constantly admitted, and insisted on, as one of the strongest reasons, why it should be adopted in lieu of the confederation.

Story goes on for like 20 pages on this topic. See volume 1 ,"book 3", chapter 3 of his commentaries (viewable on Google Books). Same stuff as he wrote in his his 1816 opinion in the Martin case.

I'll let Daniel Webster summarize. He expressed it with great clarity on the floor of the US Senate in 1830. See his "Reply to Hayne", collected in numerous places.

He has not shown, it cannot be shown, that the Constitution is a compact between State governments. The Constitution itself, in its very front, refutes that idea; it declares that it is ordained and established by the people of the United States.

...

When the gentleman says the Constitution is a compact between the States, he uses language exactly applicable to the old Confederation. He speaks as if he were in Congress before 1789. He describes fully that old state of things then existing. The Confederation was, in strictness, a compact; the States, as States, were parties to it. We had no other general government. But that was found insufficient, and inadequate to the public exigencies. The people were not satisfied with it, and undertook to establish a better. They undertook to form a general government, which should stand on a new basis; not a confederacy, not a league, not a compact between States, but a Constitution; a popular government, founded in popular election, directly responsible to the people themselves, and divided into branches with prescribed limits of power, and prescribed duties. They ordained such a government, they gave it the name of a Constitution, and therein they established a distribution of powers between this, their general government, and their several State governments.

Webster's speech came in the midst of the Nullification Crisis. So from one perspective it is of limited utility as "proof": there was a whole other side in that crisis, with a counter-argument of their own. But Webster's speech is nice because he very neatly articulates the viewpoint of the three relevant Supreme Court decisions and Justice Story's Commentaries. A good summation.

Historiography

If you're serious in asking the question (I suspect you are not), it's important to understand that in the historiography of the Civil War, this question is one of the Southern Apologist arguments. Saying that secession was legal until the Court issued its 1869 ruling in Texas v White, implies that there was no legal basis for the Court's ruling, ie it's pure judicial fiat. That's a pure Southern Apologist argument. The rest of the logic goes: "secession was not illegal until 1869, therefore secession was LEGAL up until 1869, therefore Lincoln's use of armed force to put down the slaveholders rebellion was illegal." The line of argument is used to paint Lincoln as a criminal, an aggressor, a dictator.

And it's not true. Texas v White was pure Stare Decisis: the opposite ruling would have violated previously stated law. The law underpinning the decision had been settled back in 1816.

Later Legal Commentary

There is some discussion about whether later legal commentary contradicts the argument from the 1816 and 1819 rulings. At least three times since 2000, judges have stated that the question of a state's ability to secede was unsettled prior to the Civil War. That has occurred in a Supreme Court ruling, in a Supreme Court justice's correspondence, and in a state supreme court ruling. The quotes are below. I added emphasis in each, to pull out the common idea; there is no special emphasis in any of the original docs.

• In 2004 a SCOTUS ruling (about the Pledge of Allegiance) included this in a footnote:

"At the time, the phrase 'one Nation indivisible' had special meaning because the question whether a State could secede from the Union had been intensely debated and was unresolved prior to the Civil War." ( Elk Grove Unified Sch. Dist. v. Newdow, 542 U.S. 1, 6 n. 1, 124 S.Ct. 2301, 159 L.Ed.2d 98 (2004). )

• In 2006 Justice Scalia wrote in a letter that:

"If there was any constitutional issue resolved by the Civil War, it is that there is no right to secede."

• In 2010 the Alaska state supreme court wrote that:

"While a state's ability to secede was an unsettled question before the end of the Civil War, subsequent United States Supreme Court opinions have concluded that secession is clearly unconstitutional, and Lincoln's belief in a perpetual Union is reflected in what we have described as 'a plenitude of Supreme Court cases holding as completely null' the acts of secession by Confederate states."

Is there a contradiction here?

No. It's important to note that none of these jurists (except for the second half of Alaska, after the word "subsequent") reference any legal action or court rulings. SCOTUS 2004 does NOT say, "the question whether a state could secede was unresolved prior to Texas v White." Scalia does not write, "the constitutional issue resolved by Texas v White is that there is no right to secede." The Alaska court does not say, "a state's ability to secede was unsettled before Texas v White." What they all mention is the war. All of these jurists are saying that the Civil War itself settled the question. Not any court ruling: the actual WAR. And that's the truth. Secession was not a legalistic question that the courts could settle, by examining the Constitution and accumulated Supreme Court precedent.

A good comparison is the Dred Scott ruling. There, Justice Taney intended to settle the question of slavery in the territories, and of negro citizenship. His ruling did not come anywhere close to settling that question; if anything, he inflamed the controversy. That ruling is routinely cited as one of the incidents that escalated sectional tension, in the long lead-up to the war.

Likewise secession. Secession was a political (and military!) question. No judge could "settle" it to the satisfaction of all parties. As late as the Summer of 1864, it was still an open question whether the Federal govt had the political will and support to defeat secession. Imagine if Lincoln had lost the 1864 election; it's easy to envision the winning "Peace Democrats" negotiating a peace, leaving the Confederacy in place. In that alternate hypothetical, a later SCOTUS would likely have to acknowledge that although secession might be de jure illegal, it had de facto occurred. That hypothetical Court might conclude that the US citizens had not shown a determination to maintain the Union; obviously it was possible to secede, since it had happened. It would be the opposite ruling not because the underlying law & precedents would have changed, but because the facts would have changed.

It took the WAR to settle the question of secession. That's what we see in history, and that's what the 21st century judges are commenting on.

There's nothing in the Constitution specifically allowing it. The closest any part really comes to addressing seccession is the following (from Article 4, Section 3):

Section. 3.New States may be admitted by the Congress into this Union; but no new State shall be formed or erected within the Jurisdiction of any other State; nor any State be formed by the Junction of two or more States, or Parts of States, without the Consent of the Legislatures of the States concerned as well as of the Congress.

The Congress shall have Power to dispose of and make all needful Rules and Regulations respecting the Territory or other Property belonging to the United States; and nothing in this Constitution shall be so construed as to Prejudice any Claims of the United States, or of any particular State.

The logical conclusion of this is that the disposition (eg: selling or seccession) of USA territory has to involve Congress. So if a state wants to take its territory out of the USA, it would have to get Congress to agree.

In reality though, the legality of seccession is part of what the Civil War was fought over. The South lost, so no it wasn't legal. :-)

My answer is similar to E1Suave's, but my interpretation is different.

Texas v. White, 1869, explicitly addressed this issue. The US Supreme Court ruled that the Texas secession of 1861 was unconstitutional, and had never been valid. The ruling was based on the US Constitution (not on any amendments ratified after 1861). According to the ruling, secession was illegal both at the time of the ruling (1869) and at the time Texas attempted to secede (1861), and in fact at any time after Texas joined the union in 1845.

The actual substance of the case involved some US bonds that were held by the State of Texas and were sold by the Confederate state legislature. The court resolved the issue by ruling that the action of the Confederate state legislature was invalid, and the bonds were still owned by the State of Texas.

I've thought of another argument, one that the court did not use as far as I can tell. The Constitution defines the procedure for admitting new states. It defines no such procedure for secession, which if it were legal would require various actions by the Federal government, such as removing Senators and Representatives. Since the Constitution does not grant Congress the power to accept secessions, one could argue that it has no such authority, and therefore states cannot legally secede.

The authors of the Constitution could easily have established a procedure for secession if they had wanted to.

One could certainly argue that Texas v. White was decided incorrectly, but the current legal precedent is clearly that states may not unilaterally secede, and that precedent states that unilateral secession has always been illegal.

EDIT :

I think there's been some confusion about the word "illegal". It commonly refers to an act that is punishable under criminal law, but the question regarding unilateral secession is whether it's authorized by the Constitution. We commonly refer to unconstitutional actions as "illegal"; perhaps that's insufficiently precise.

I'd say the real question here is whether unilateral secession is permitted by the Constitution. Given that question, the principal of nulla poena sine lege is irrelevant, since it's not a matter of a criminal law for which violators may be punished.

For example, there is no punishment specified for passing a law that restricts free speech, but any such law is invalid.

Texas V. White clearly expressed the Supreme Court's opinion that unilateral secession was illegal in 1861, when Texas attempted to secede. There is no ambiguity in the Court's ruling. There are valid arguments that the Court's ruling was incorrect, but any such arguments should start with an acknowledgement of what the ruling actually said.