There is a mechanism to resolve those matters: referendums. Once again your arguments are left wanting. Messy and difficult internal politics surrounding fundamental issues does not allow the invasion of a neighbour.

Crimea didn't need daddy Russia to forcibly integrate it into the Russian state. It could have done that all its own if it had wanted. The fact Russia has to lower itself to violence to integrate territory illustrates how poor its logic is.

But then 2014 happened, and everything changed. Once you choose to ally yourself with a foreign power that is aggressively attacking the larger nation you are attempting to secede from -- as the political establishment of the ASSR did at the time -- your moral claim to independence (a key being always an assurance that you will never do harm to that nation) is instantly invalidated.

And when that foreign power you are seeking to ally with also happens to be the one that genocided a large chunk of your indigenous population -- not centuries ago; but in living memory -- that claim is nullified even further.