My fundamental belief here is that the norms on a countries borders should be decided by referendum, and then respected (i.e. not invaded).
If you think borders should be decided by referendum then you should endorse a substantive right to having a referendum in the first place. That implies that Crimea should be able to hold a referendum even if Kyiv refuses to allow it.
The 2014 referendum was one month after Russia invaded Crimea. I wouldn’t trust the results of it (a 96% result to join Russia is implausible)
See the link I provided to my other post discussing public opinion in Crimea. The result is plausible when considering that most pro-Ukraine Crimeans boycotted the vote (so true support was ~80%), but more importantly, ignoring Russia’s untrustworthy referendum, polling data shows majority support for annexation. I have no doubt that in 1991 a slim majority of Crimeans wanted Ukraine to leave the USSR, but it’s far from the best evidence we have about how Crimeans in 2014 felt about leaving Ukraine to join Russia.
If you think borders should be decided by referendum then you should endorse a substantive right to having a referendum in the first place. That implies that Crimea should be able to hold a referendum even if Kyiv refuses to allow it.
See the link I provided to my other post discussing public opinion in Crimea. The result is plausible when considering that most pro-Ukraine Crimeans boycotted the vote (so true support was ~80%), but more importantly, ignoring Russia’s untrustworthy referendum, polling data shows majority support for annexation. I have no doubt that in 1991 a slim majority of Crimeans wanted Ukraine to leave the USSR, but it’s far from the best evidence we have about how Crimeans in 2014 felt about leaving Ukraine to join Russia.