What was the consequence of Gestapo being declared a criminal organization in the Nuremberg trials in 1945?

#tl;dr

Until 1947 it was dry cookie time. Until 1950 they were barred from being public servants, if in tier 1 and 2 category of "being nazi". After 1951 they got all the love for being loyal Germans, American allies and trustworthy anti-communists. The shadow of the past only befell few individuals, who after some kind of fall from grace were dragged into the spotlight.

The other answer speculates around, and has no sources. That is intolreable. So we have to rectify the desinformation en route in this answer (wrong answer is quoted by preceding "OA")

OA The 2 million figure is highly misleading. It includes the entire membership roster of the NSDAP, most of whom were simply citizens living and working their everyday lives.

Wikipedia reveals that the NSDAP had ~8.5 million members. "Living their lives" really meant denouncing Jews, 'Aryanising' their property, snitching on neighbours, 'using' slave labour, either from concentration camps of prisoners of war, or forcefully recruited from occupied countries. Plundering the economies of Greece, Denmark, etc…

OA Nobody was going to arrest and imprison all of them.

Somehow true. But this is misleading.

One of the goals after the defeat of nazism and Germany was de-nazification. Not only 'Nuremberg' but 12 other allied trials went on. Based on Control Council Law No. 10, CCL10. Ideally, all Nazis were to face at least a Spruchkammer.

There, they would all state 'to have been in the resistance', sometimes in hiding. As Werner Finck famously put it: some hiding so well that the rest of the world believed them to be Gauleiters. Getting the desired [Persilschein]6. But some were indeed convicted. Category 1 and 2 being sent into labour camps or prison.

Even pre-existing German law had and has §129 membership in a criminal organisation. Which of course meant in Germany from Kaiser's time onwards being a socialist. Or social democrat. Rarely things like Mafia or the like.

Already during the IMT it was declared:

" Each of the following acts is recognised as a crime:
" (d) Membership in categories of a criminal group or organisation declared criminal by the International Military Tribunal. […] In effect, therefore, a member of an organisation which the Tribunal has declared to be criminal may be subsequently convicted of the crime of membership and be punished for that crime by death. […]
Since the declaration with respect to the organisations and groups will, as has been pointed out, fix the criminality of its members, that definition should exclude persons who had no knowledge of the criminal purposes or acts of the organisation and those who were drafted by the State for membership, unless they were personally implicated in the commission of acts declared criminal by Article 6 of the Charter as members of the organisation. Membership alone is not enough to come within the scope of these declarations.
_{— Judgement : The Accused Organizations, Avalon Project, Yale Law School}

The goal and intent was to be able to convict higher echelons, not directly shooting other people, and lower ranks, who ensured smooth operations. The French delegation brought froward the idea to the United Nations War Crimes Commission in 1943 and it was expanded by Murray Bernays. This in order to reverse a principle: this time membership implied being guilty until proven innocent. As the bolded parts in the above quote shows, that wasn't upheld.

As regards actual convictions of membership, all but one of the defendants in the Pohl case were charged under Count 4 with being members of the SS, an organization declared criminal by the Nuremberg Tribunal.

The U.S. Military Tribunal hearing the case keenly stressed the presumption of innocence, that “every defendant in a criminal case is presumed to be innocent until the prosecution by competent and credible proof has shown his guilt to the exclusion of every reasonable doubt.”

Oswald Pohl had been the administrative head of the SS for eleven years, directing and administering its affairs, as well as being in charge of the administrative aspects of all concentration camps. Applying Control Council Law No. 10, the U.S. Military Tribunal found him to be a member of a criminal organization “under the conditions defined by the judgment of the International Military Tribunal.”

Ten of the accused in United States of America v. Karl Brandt et al. were convicted on the charge of membership in the SS, in addition to other counts. The defendant Poppendick “remained in the S.S. voluntarily throughout the war, with actual knowledge of the fact that that organisation was being used for the commission of acts declared criminal by Control Council Law no. 10.”

Those convicted of SS membership were thereby, according to the U.S. Military Tribunal, “criminally implicated in the commission of war crimes and crimes against humanity.” Fifteen years after the Nuremberg trial, Adolf Eichmann was convicted by the District Court of Jerusalem on charges that included “membership of a hostile organisation.” He was found to have been a member of the SS, the SD, and the Gestapo, organizations declared criminal by the IMT.
Since the Second World War trials, the concept of criminal organizations has not been revived under international criminal law…
_{— Shane Darcy: "Collective Responsibility and Accountability Under International Law" (ch5 Criminal Organizations, pp257–292. excerpt), The Procedural Aspects of International Law Monograph Series Volume 27, Transnational Publishers/Brill: Leiden, 2007.}

If one looks at the Allies' plan to punish National Socialist macro- and mass criminality by means of international criminal law as well, and to take into account the broad social anchoring of National Socialism in criminal law, the developments outlined here in the post-war years will lead to an overall sobering balance. In the legal and legal-historical literature as well as in the literature on contemporary history, judgments predominate which not only deny - and often welcome - the success of the legal figure of the "Criminal Organization" for the period immediately after 1945 in terms of punishment policy, but which also take a sceptical view of the benefits of the legal figure as a whole. When the United Nations prepared the Genocide Convention in 1947/48, the Soviet negotiators suggested that organizations that committed or called for genocide should also be punished, but they were unable to assert themselves.
_{— Eckart Conze: "'Verbrecherische Organisation' Genese, Anwendung und Reichweite einer Rechtsfigur", pp217–238, in: Johannes Hürter & Michael Mayer (Eds): "Das Auswärtige Amt in der NS-Diktatur", Schriftenreihe der Vierteljahrshefte für Zeitgeschichte Band 109, Walter de Gruyter: Berlin, München, Boston, 2014.(PDF)}

At the latest after the Americans had another fit of Red Scare and saw the Soviet Union as a bogeyman they practically dropped all pressure on any nazis. Already during the first Nuremberg trials they correctly identified nazis as anti-communist and re-instated their standing as 'most-beloved allies' as well.

Not only paperclip nazis, needed for bombs, planes and moonshots, but especially hardened criminals like Reinhold Gehlen:

Allegiance: Weimar Republic (1920–1933), Nazi Germany (1933–1945), United States (1946–1956), West Germany (1956–1968)

In 1968 it then came to this punishment:
.

In short: Every Nazi was useful to the Americans after 1946. Gehlen being the founder and to this day guiding spirit of the German secret service BND. Second picture shows his Post-war West German medals and honours, including the highest there is.

Being a nazi was a perfect letter of recommendation for post-war society. Unofficially of course. You know: appearances. People like Heusinger, in Hitler's general staff:

^{Bundesarchiv Bild 183-B24543, Hauptquartier Heeresgruppe Süd, Lagebesprechung.jpg}

even became Heusinger, chairman of the NATO Military Committee. Others went on to join the 'new' government, like Globke.

SS members like Schleyer also knew no limits for upward success, him becoming "Industrial leader in West Germany". That list is almost endless. But some people were listed in books like Braunbuch or "Hitler went, they stayed". Willy Winkler: "Das braune Netz. Wie die Bundesrepublik von früheren Nazis zum Erfolg geführt wurde", 2019; Felix Bohr: "Die Kriegsverbrecherlobby. Bundesdeutsche Hilfe für im Ausland inhaftierte NS-Täter", Disseration, Berlin 2018.

Filbinger, Kiesinger, Schmidt, Weizsäcker were political leaders (minister president, chancellor, president of West Germany) who participated in war crimes, were party members or made the justice system into terror. Karl Carstens, president of the West German republic, was SA from 1934, applied for party membership in 1937. Spruchkammer ruled that to be a sign of resistance…

Rudolf Diels, head of Gestapo 1933, one of the conspirators and collusionists around the Reichstag-fire, SS-captain, imprisoned by Americans 1945, then working for them, wanted by Soviets, protected by Western allies, presented himself as 'resistance' before the Spruchkammer, then went into government of Lower Saxony in 1950, received ample pension until his death.

Werner Best had a little bit more trouble, being sentenced to death in Denmark 1948, which he outlived until 1989.

Max Wielen, Gestapo man who was responsible for killing the "Great Escapers", released in 1952.

Erich Priebke Gestapo Italy and personally responsible for massacres just escaped British internment, took a new name and lived 50 years in Argentina. Got himself a German passport in 1952. In 1995 and 1998 on trial in Italy. Because of "ill health" only convicted to house arrest, which was not really enforced. In 2010 he was prepared as candidate for becoming the German president. (By one of the numerous nazi parties operating in Germany now.)

Siegfried Buback, NSDAP since 1940, became attorney general, helped bring down the first social democratic chancellor, and made first headlines in the Spiegel affair, albeit failing to strangle freedom of the press in West Germany.

Until recently, receivers of the "Bundesverdienstkreuz" were practically always nazis.

OA The cadre of the GeStaPo other organisations could face trial if identified and apprehended, but many of them too would simply be people like file clerks, not interesting to the tribunals.

What that might mean is underdetermined. All should have faced some form of trial and punishment.

Lower ranks only got very lucky as until 1947 the allied went after the big heads. Some fled via rat-lines, others trusted the West-German state to protect them. Even people like Alois Brunner, and Eichmann himself were protected by state officials and other industrial leaders.

That is not in the least because civil service, BND, Verfassungsschutz and police on all levels were usually hardened nazis, grooming their offspring in their image and fostering young talents into the 'right' way.

The [North Rhine-Westphalia LKA was revealed two days ago to have had 4 out of 6 Führers]55, that is 'directors', who were known criminal nazis, not mere members, but those with proven personal guilt. The current directors and the public claim to be appalled and surprised, yet the leading researcher is evaluating that as "not an atypical finding".

When a prominent person fell into disgrace, for whatever reason, then his membership in various organisations or even his personal criminal activities, like torture, killings, gassings, burning of villages etc made headlines.

Serge and Beate Klarsfeld, Simon Wiesenthal were private individuals who had to go on a veritable crusade against the murderers and state terrorists. Precisely because mainly Americans and Nazis in Germany colluded so well after the wall.

Compromising material was always useful for those in power. But files disappeared, archives just lied to inquirers. But legitimate research and even prosecution is still hampered. For example the contents of the Gestapo-Personenakten der Leitstelle Düsseldorf are now fully digitised. But looking into them requires a special permission, this time citing right to privacy laws and special protection of the names contained therein.

People like Klaus Barbie, Gestapo chief of Lyon went on to be

After the war, United States intelligence services employed him for his anti-Marxist effort

In most cases, even after coming to prominence, and being charged, or convicted in absentia, Germany refused to render known and proven war criminals to justice. The official sentiment is perhaps best illustrated by the German state increasing the pension of the widow of people's court judge Roland Freisler after a few years. She had to sue for that, but the judges then argued in her favour. "As his unqustionable qualification would have led him to pursue a great career in post-war society"!

That this is an accurate assessment is demonstrated by Kurt Lischka, Gestapo, SiPo and SD in Paris, convicted in absentia in France to life imprisonment, living free under own name in Germany, became a judge! Just because the Klarsfelds made a big fuss he was dragged before another judge in 1980.

OA Many in the SS were simple field soldiers in the Waffen SS, as well as people like cooks, nurses, clerks, more uninteresting targets except maybe for questioning.

Yeah? You need a cook to keep the gasman fed? Or a clerk to count the kills? Oskar Gröner is just such a case:

His responsibilities included counting and sorting the money taken from prisoners, and he was in charge of the personal property of arriving prisoners.

The swift justice of Germany took care of him already in 2015! Another 'innocent SS' from the KZ Stutthof was charged with murder in 36000 cases in 2018.

OA And then there's the inevitable overlap. Every SS volunteer was also a Party member, as were most if not all GeStaPo employees, every single SA man (the SA of course no longer existing after the night of the long knives), and pretty much everyone else on the roster of the mentioned organisations.

It is unclear what that should mean or what may follow from that. "Being SS was 'criminal organisation' but being NSDAP also means: that would cancel out"? Then the factual errors of course: The SA existed long after that night in 1934 ("Dissolved May 8, 1945").

OA So yeah, they'd not go after everyone. It'd be impossible logistically, would take way too much manpower and prison space to lock up millions and interrogate them. Lower ranking members, unless there were specific accusations against them, were likely either ignored entirely or just taken in for a round of questioning and then released.

In reality, all were supposed to be questioned. Most were, somehow. Until 1950 they had a hard time getting into official state service. Then that changed.

In 1951 West Germany made the Law: Gesetz zur Regelung der Rechtsverhältnisse der unter Artikel 131 des Grundgesetzes fallenden Personen. Which meant that even higher ranks returned to their duty: hunting down communists, h*m*sexuals, the lot. Only Jews weren't such a popular target by then.

The Federal Criminal Police Office (Bundeskriminalamt) started with this roster of qualifications:

^{Data source: — Dieter Schenk: "Auf dem rechten Auge blind: Die braunen Wurzeln des BKA", Kiepenheuer & Witsch, 2001.}
Showing that in 1954 being in either the criminal organisations of SS, SD or Gestapo, or multiple of these organisations, including Einsatzgruppen death squads was probably less of a hinderance but 'a plus' to get into such office. Note: most of the 'clean' boxes in this diagram are simply empty! Worth a special mention is Kurt Griese: SS, NSDAP, NSV, SiPo, Einsatzgruppen. Obviously de-nazified as just a bystander. So un-nazi that upon joining the BKA he quoted NS-regulations to argue how all former nazis could join, even regardless of other qualifications. An argument readily accepted by the ministry.

The few trials that did go on then were focussed on individual high crimes. The judge and prosecutor Fritz Bauer had a very hard time to prosecute nazis, like he managed to do in the most prominent Frankfurt Auschwitz trials. Being a Jew, a h*m*sexual, he faced just all the prejudice that was present before 1945. He was sabotaged, defamed and blackmailed by former Gestapo members, those now working for the state again.

The older comrades had indeed something to fear. State protection could fail if spotlight illuminated the wrong areas. Some more egregious cases went on trial. But mostly not for being a member, but for accusations grounded on personal and individual guilt in criminal behaviour. The previously cited law §129 was practically reserved for left-wing activists.

The former members made themselves useful in the official state: inofficial NATO stay behind networks (Gladio), founded a few parties (SRP, NPD, Republicans), infiltrated other parties (CDU, CSU, FDP, DP). For folkloristic gemütlichkeit and more, protection, they also constructed clubs like Bund Deutscher Jugend (for fighting Russians), a couple of Landsmannschaften (for re-conquering Poland and Czechsolovakia, after 1945)…

The founder of the Republican party Franz Schönhuber illustrates nicely how careers went: Hitler Youth, party member, SS, applied for Leibstandarte Adolf Hitler, then served as instructor for French SS, iron cross 2nd class. Spruchkammer verdict: low tier "Mitläufer" (mere follower).

Became editor for a number of newspapers (Münchner Abendzeitung, Deutsche Woche, tz). Then joined Bavarian state television, became chief of information section. Made possible because the right-wing state party CSU controlled the government, and the broadcaster. And he was very good friends with that party as well, but for appearances he was counted as being social-democrat leaning. Became chairman of the Bavarian Journalist association, member of the German press council. Wearer of the Bavarian order of merit.

When he published then an autobiographical book in 1981 ("I was there/went along") which pretty much glorified the war, national socialism and the SS, some people had enough. That is they asked him to resign his chairmanship, offering him instead "honorary chairman". A libel court case came to the verdict that the book would be proof of his distance to right-wing ideology. (How ridiculous this verdict is? See here)

He went on to prove that verdict right by founding the right-wing extremist Republican party, because the Nazi party NPD was 'too far left' in his eyes.

In his book he praises the meritocracy, the cameraderie, the revolutionary spirit, the fairness, the lack of arrogance, the innovation, the loyalty and the internationality:

… that the best elements of fascism fought in these [foreign] divisions [of the Waffen-SS], […] They were marked by the democratic traditions of their home countries. […] Apart from a few adventures and eternal mercenaries, they flocked to the units in order to secure their fatherlands a better place in the new order of Europe
_{— (Schönhuber, p. 153).}

^{— Republican party rally 1992, chairman, text reads: "America Germany first" src}

Isn't that nice?

In case of present legal danger or just looming trouble, they also created Stille Hilfe or the HIAG (Mutual aid association of former Waffen-SS members"). If anyone survived the short term in the aftermath of the war, after 1951 the most probable outcome in life was good, if not much better.

Denazification: In late 1945 and early 1946 […] the western powers and the United States in particular [lost] interest in the programme. […] Denazification was carried out in an increasingly lenient and lukewarm way until being officially abolished in 1951. The American government soon came to view the programme as ineffective and counterproductive. Additionally, the programme was hugely unpopular in Germany and was opposed by the new West German government of Konrad Adenauer.

For hard numbers: in the American zone 3 623 112 nazis criminals were registered and 'eligible for questioning'. 950 126 were really looked at. The rest of the cases were not processed, 2 504 686 ending in amnesty. In all Western zones the category 1 and 2 nazis came in at 0.7% of all cases looked at, roughly a third deemed mere follower and roughly a third cleared.

_{— Justus Fürstenau: "Entnazifizierung. Ein Kapitel deutscher Nachkriegspolitik", Luchterhand: Neuwied, Berlin, 1969, p227. quoted from "Aufgliederung der Entnazifizierungseinstufungen in den westlichen Besatzungszonen (1949-1950)"}

The very different numbers show not a different geographical distribution of nazis, but an extremely differing policy between the Western allies on that.

While the American zone may seem harsh in comparison, in reality as early as 1948 they allowed 14400 nazi civil servants to return to their posts.

— Sebastian Römer: "Mitglieder verbrecherischer Organisationen nach 1945: Die Ahndung des Organisationsverbrechens in der britischen Zone durch die Spruchgerichte", Peter Lang: Frankfurt, 2005.

— Niklas Frank: "Dunkle Seele, feiges Maul. Wie skandalös und komisch sich die Deutschen beim Entnazifizieren reinwaschen", Dietz: Bonn, 2016.

In the West the same brown Seilschaften held together that had been in power before 1945. As everywhere in Bonn's federal government, the proportion of former NSDAP members even continued to rise into the 1960s.

At the end of the Adenauer era all six department heads of the Federal Ministry of the Interior had joined former 'party comrades', one of them additionally a member of the SS and five of the SA - all in 1933.
_{— Frank Bösch & Andreas Wirsching (Eds): "Hüter der Ordnung. Die Innenministerien in Bonn und Ost-Berlin nach dem Nationalsozialismus", Wallstein: Göttingen 2018.}

The proportion of former NSDAP members in the Bonn ministry: 70 percent. Historians looking at the foreign office, its members and actions from 1933–1960 conclude that the Nuremberg IMT clearly missed to label this institution as another 'criminal organisation', which took great care to save posts for nazis within it after 1949…

— Eckart Conze, Norbert Frei, Peter Hayes, Moshe Zimmermann (eds): "Das Amt und die Vergangenheit. Deutsche Diplomaten im Dritten Reich und in der Bundesrepublik", Karl Blessing, 2010.