What was of dubious legality was the Soviet regime, which exterminated the "kulaks" and between 2 to 7 million Ukrainians, and also German and other peoples who had taken up residence there.
Regarding Crimea .........there is a long history of Crimea trying to get it’s Independence from Ukraine:
This is sad defense for a fraudulent and corrupt election. Russkie soldiers, armed with grenade launchers, marched in a fringe Russian-Annexation party leader (with 2 members in the Crimean rada), who was also a member of the Russian mafia (which is populated by "former" KGB), and was made Prime Minister on the spot, without any election.
The Referendum that he declared afterwards was launched through 1) Complete control of media with constant lies. 2) Little kids voting. 3) Ballots being trucked in apparently already filled out with a "yes" vote. 4) People being disappeared from off the street, tortured to death, and their bodies found in the woods later. 5) Russkies marking Tatar houses to remind them of Soviet purges.
And the result of something like 80 or 90 percent in favor was impossible, because even the very best polls that had been taken in the area showed that they were, at best, split between independence (and thus annexation) and not, with 30 percent of the population, at the very least, guaranteed to always oppose it.
As for the "dubious" legality of giving Crimea to Ukraine. Crimea is geographically connected to Ukraine. It is the Soviet regime, which killed between 2 to 7 million people in Ukraine, including ethnic Germans and others, and colonized the land, that is of dubious legality.
Nothing sad about it...Crimea got what they wanted after years of trying. (Remember this without a gun fired) And the celebrations rose for finally being back where they wanted to be...”Home” to them....and Putin got paid off for what we will soon be seeing in E. Ukraine.....after all he isn't going to stop that fighting until he is paid...and it won't be just Crimea....it'll be South-Stream pipeline and any other deal that's struck for him to use his forces to calm the waters.
As for fraudulent voting.....that's not even worth a response considering how our own elections go.