The last stages of the Soviet collapse.
Now the last surviving “big country” Ukraine is going through the same thing and people want to get up in different beds.
What they have in common is a country on its deathbed. That happened to the Soviet Union and its happening now to Ukraine.
It is of dubious constitutionality? Sure, the dissolution of the Soviet Union was technically illegal. So is the dissolution of Ukraine.
But the Maidan regime is discovering, like the Soviet junta before it, that calling out the tanks won’t preserve the union.
Might still makes right, as it always has.
Not sure if you want to go there. The Baltic Republics were never legally incorporated into the Soviet Union in the first place.