American presidents on secession legality?

I think you are asking the wrong question. The legality of secession or not wasn't the driving reason why the Union went to war. Secession itself was the unacceptable lever which moved Abraham Lincoln to war. The legality is murky and inconclusive. Put to an impartial tribunal, the South had a pretty convincing argument. Lincoln did not care. What Lincoln was focused on was the Federal Papers. Specifically #6-10 where the founding fathers (Hamilton Madison and Jay) warn against secession as one of the worst catastrophes which could befall the nation. Europe had fought wars for 1000 years because two equally matched countries existing side by side would naturally compete religiously, culturally and economically and that by the European example meant endless war. That is why Lincoln went to war, his second worst outcome to the crisis. Lincoln could not permit the South to just leave the union.

As for the rest of your answer.. I gave the presidents' views below.

George Washington June 8, 1783 - strongly opposed secession.

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.

Thomas Jefferson(March 4, 1801) in his First Inaugural Address said - Believed it was Legal and reasonable action.

“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.”

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

• Madison went back and force between Washington and Jefferson. He broke with Jefferson over ratification of the Constitution, and broke with Jefferson over Shay's rebellion. Jefferson did not think the Federal Government should send troops to put down Shay's rebellion. Madison did defend a state's right to leave the union, though, in debates over the Constitution.

“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.”

James Monroe (1814) (*) Not a Quote, but in the war of 1812, parts of New England tried to secede. Monroe ordered troops (23rd and 25th regiments) into Hartford Conn, where a convention on dissolution was being held by secessionist federalists in order to put down secessionism.

(*) see seventh paragraph under "Restoring Government and Peace"

Andrew Jackson. You already have a good quote.. But I have another one for you. Jackson had to deal with his own secessionists. South Carolina had threatened to secede over taxes(tariffs).. this brought on the Nullification Crisis, where South Carolina declared the tariffs Null and Void inside their state and threatened to leave the Union. To which Jackson Responded.

if one drop of blood be shed there in defiance of the laws of the United States, I will hang the first man of them I can get my hands on to the first tree I can find.’

Jackson's VP was from South Carolina, advocated secession, and was in the room when Jackson delivered that line, Jackson looking squarely at his VP.

When Robert Hayne ventured, ‘I don’t believe he would really hang anybody, do you?’

Thomas Hart Benton responded

‘Few people have believed he would hang Arbuthnot and shoot Ambrister(*) . . . I tell you, Hayne, when Jackson begins to talk about hanging, they can begin to look out for ropes!’ In January 1833,

(*)two British subjects charged with aiding Seminole and Creek Indians against the United States. Jackson captured them in Florida, and over British and Spanish protest executed both after giving them a trial which he presided over.

Martin Van Buren, supported President Lincoln's decision to resist secession with force. Martin Van Buren died in 1862, at age seventy-nine.

William Henry Harrison was pro slavery but against secession.

The only legitimate right to govern is an express grant of power from the governed.

His presidency was the shortest. He gave a two hour (longest) inaugural speech without a coat or a hat to show that while 67 (oldest president to that point) he was still hardy.. He caught pneumonia and died a month latter.

John Tyler. As a senator, he broke with his party and opposed Jackson's use of force against South Carolina. This ultimately lead to his resignation from the senate 1836. Which cemented his appeal to Southern Democrats.. Which made him an attractive VP for William Henry Harrison, which allowed him to become president when Harrison died first month in office. John Tyler Quote from 1836 in his resignation letter to then VP Martin Van Buren.

I shall carry with me into retirement the principles which I brought with me into public life, and by the surrender of the high station to which I was called by the voice of the people of Virginia, I shall set an example to my children which shall teach them to regard as nothing place and office, when either is to be attained or held at the sacrifice of honor.

When the Civil War broke out, Tyler, who was from Virginia, initially tried to broker a peace between the North and South. When his efforts failed, Tyler became a secessionist and a Virginia delegate to the provisional Confederate Congress. Tyler was elected to the Confederate House of Representatives later in 1861. However, he died on January 18, 1862, before he could serve in the Confederate House.

James K. Polk Condemned Secession and supported Jackson's Force Act.

Zachary Taylor In February 1850, after some incensed southern leaders threatened secession, Zachary angrily told them that he personally would lead the army if it became necessary in order to enforce federal laws and preserve the Union.

Millard Filmore During the American Civil War, Fillmore denounced secession and agreed that the Union must be maintained by force if necessary, but was critical of the war policies of Abraham Lincoln.

Franklin Pierce was a northern Democrat who saw the abolitionist movement as a fundamental threat to the unity of the nation. His polarizing actions in championing and signing the Kansas–Nebraska Act and enforcing the Fugitive Slave Act failed to stem intersectional conflict, setting the stage for Southern secession.

Inaugural Address (4 March 1853).

The storm of frenzy and faction must inevitably dash itself in vain against the unshaken rock of the Constitution. I shall never doubt it. I know that the Union is stronger a thousand times than all the wild and chimerical schemes of social change which are generated one after another in the unstable minds of visionary sophists and interested agitators. I rely confidently on the patriotism of the people, on the dignity and self-respect of the States, on the wisdom of Congress, and, above all, on the continued gracious favor of Almighty God to maintain against all enemies, whether at home or abroad, the sanctity of the Constitution and the integrity of the Union.

James Buchanan expressed the view that it was illegal for the seven states to secede, but he also felt that it was illegal for the federal government to take any steps to halt secession. Buchanan believed, and would so maintain to the end of his life, that the problem was caused by the actions of the Northern abolitionists. No plan was forthcoming from the president, who eagerly awaited the inauguration of Abraham Lincoln. Under Buchanan's presidency, his Secretary of War, John Floyd, a Virginian, turned over large stockpiles of arms to officials in the seceded states. Arsenals and forts were seized by state officials, while the Buchanan Administration did little to counter.