Donald Trump has called for the US constitution to be terminated. Apart from something akin to a civil war or dramatic societal upheaval, is there a mechanism which could enable the termination of the US constitution?
The US constitution — like all national constitutions, to my knowledge — is considered a foundational document. It may be amended by Congress (subject to judicial review) or through a new constitutional convention, but it cannot be terminated in part or whole except by ending the US system of government and replacing it with something else.
It's worth noting that Trump did not precisely call for the termination of the US constitution itself, but merely those rules and regulations that forced him out of office and prevent his (immediate) reinstatement. And I'm not entirely convinced that he has any interest in or understanding of the constitutional issues in play here. Like most things Trump, this comment suggests narcissism more than nefarious intent. For Trump, the Constitution is much like the Bible: something to be held up for photo-ops and used to browbeat opponents, but otherwise of no significance whatsoever.
...because it's happened before.
You have no doubt heard of the Articles of Confederation, which were in effect for most of the 1780's, before the Constitution. They included a requirement that any changes to them required unanimous approval of the states.
No change to the Articles happened. Instead, the states (roughly) just collectively decided to stop doing that, and have a Constitution instead.
Documents like the Articles and the Constitution are only in effect as long as everyone collectively believes they are.
Practically though, there's no chance. We have a good thing going with the Constitution, which is why it has survived so long with so few changes. For all the grumbling, popular sentiment has remained firmly with the status quo (for quick comparison, the last time that wasn't true saw three major amendments passed in quick succession).
Trump has zero chance of overturning that.
Article V of the Constitution provides two ways to propose changes to the document. Changes may be proposed either by the Congress, through a joint resolution passed by a two-thirds vote, or by a convention called by Congress in response to applications from two-thirds of the state legislatures. These processes likely can used to instantiate a completely new Constitution.
Constitution is also unlikely to survive a complete loss of a war with occupation and annexation following. This could be something like China or Russia, even it would not be easy for them to win a war.
I am not fully sure which of these two ways Trump is currently envisioning.
Apart from something akin to a civil war or dramatic societal upheaval, is there a mechanism which could enable the termination of the US constitution?
The kind of termination of the constitution as described by Trump in his post would be, in legal terms, an illegal seditionist insurrection. There is no legal way to do that.
Trump as he often does, is "coloring outside the lines" of what is permitted by law.
It only works if you believe in it
Other answers have covered the possible legal mechanisms. But apart from those, no constitution is stronger than the peoples will to adhere to it. If
a) Mr Trump (or really any other hypothetical person) said "Never mind the fine print. I rule!" and
b) Enough people with enough power and influence actively or passively supported that claim.
Then the constitution would, in effect, be terminated.
This would have to be through the amendment process, certainly, which is laid out in Article 5. But there is also a giant stumbling block I've highlighted below.
The Congress, whenever two thirds of both Houses shall deem it necessary, shall propose Amendments to this Constitution, or, on the Application of the Legislatures of two thirds of the several States, shall call a Convention for proposing Amendments, which, in either Case, shall be valid to all Intents and Purposes, as Part of this Constitution, when ratified by the Legislatures of three fourths of the several States, or by Conventions in three fourths thereof, as the one or the other Mode of Ratification may be proposed by the Congress; Provided that no Amendment which may be made prior to the Year One thousand eight hundred and eight shall in any Manner affect the first and fourth Clauses in the Ninth Section of the first Article; and that no State, without its Consent, shall be deprived of its equal Suffrage in the Senate.
If "termination" means here the complete dissolution of the Constitution itself, that would mean the dissolution of the U.S. Senate as well. The new Senate (if there is one, who knows!) would be a spiritual successor to our senate, but it would not be THE Senate referred to in Article 5.
This sets us up for an constitutional crisis based on two, equally plausible readings of "equal suffrage." Pro-termination lawyers would argue that since all states have been set to zero seats, "equal suffrage" has been preserved. Anti-termination lawyers would say that "equal suffrage" requires the existence of suffrage in the first place. I'm inclined to say the anti-termination lawyers have the better case: no one says with a straight face that totalitarian states enjoy "equal suffrage" when choosing their leaders.
So for everything to be absolutely airtight, I think we'd have to see the following:
An amendment proposed through Congress or a convention called by state legislatures.
The amendment passes all 50 states, and not the 3/5ths generally required.
But the other thing to keep in mind here is that strict legality is often an afterthought when countries get rid of their constitutions (and is almost certainly an afterthought for Mr. Trump). Even the U.S. Constitution itself blatantly contradicted the Articles of Confederation when it was enacted; the Constitution laid out that it'd become law when 9 of the 13 states ratified it, while the Articles required unanimous agreement for changes. It ended up being moot, but if there had been one or two holdout states it could've been the setup for a major legitimacy crisis.
This requires having one party — with complete loyalty to itself but no loyalty towards ideas like “democracy” or “justice” — winning 2/3 of the seats in the Senate (a high bar which has not been met since 1967), plus a simple majority of the House.
Then, for anyone in the federal government who opposes your agenda — on the Supreme Court, in Congress, or in the Presidency (if the other party won somehow) — you impeach them. It doesn't matter what the charge is, or how tangential the accused's involvement is. Just come up with some reason to get rid of them. “High crimes and misdemeanors” doesn't have a precise definition, and the standard of proof is left to the discretion of Congress itself. All you need is the right number of votes.
You now have a legal one-party dictatorship. The Constitution is still nominally in effect, but feel free to ignore it. The Supreme Court (what's left of it) is on your side, so they're not going to stop you.