Crimea was illegally annexed by Ukraine, so why shouldn’t Crimea separate from it?
What part of this is illegal?
Crimea and adjacent territories were united in the Crimean Khanate during the 15th to 18th century before falling to the Russian Empire and being organised as its Taurida Oblast in 1783. In 1954, the Soviet Crimean Oblast was transferred from Russia to Ukraine. It became the Autonomous Republic of Crimea within newly independent Ukraine in 1991, with Sevastopol having its own administration within Ukraine but outside of the Autonomous Republic.To the extent that the conquest and annexation of Crimea to the Russian empire was legal, its transfer to Ukraine by that same Russian empire was also legal.