@xerx, I'm constantly amazed at how legal and proper you are. Your instincts are very different from mine, and I admire them.A'ight, I'll need to read more about the subject. It's pointless to have an opinion about stuff like this without doing (lots of) research.
It's entirely possible that Nuland's telephone conversation was completely taken out of context. I also know for a fact that Yanukovich was indeed voted out of office by the Ukrainian parliament following Euromaidan, not somehow removed at gunpoint, and that his removal wasn't necessarily illegal (although, again, I'm out of my depth when discussing the legality and legitimacy of this move).
But I'm going to look for a more objective source. This author seems biased, and she glosses over some things when dismissing Donetsk and Luhansk's case for independence:
She describes the Donbass republics as "gangster states", citing their criminality and corruption (I can believe this, and I somewhat doubt that these problems will be quickly solved by joining Russia). But it isn't immediately obvious that their criminality and corruption were far outside the norm compared to other parts of Ukraine, in case that's her implication. And even if they were criminal and corrupt, I don't see why a region's internal problems would affect its legal case for independence under international law.
She says that the rest of Ukraine, including its Russian-speaking regions (which also disapproved of the post-Euromaidan government), were opposed to the secession of the Luhansk and Donetsk republics. But she doesn't provide legal reasons for why one region's disapproval would negate another region's case for independence. In a recent instance, the International Court of Justice ruled that Kosovo (which was also in conflict with the Serbian central government and barred from independence under Serbian law) was legally allowed, under international law, to unilaterally declare independence from Serbia (1). I don't know for sure if these (and other) cases for independence are similar, but it seems like an important question to tackle.
When discussing the war in Donbass, she condemns but glosses over Ukraine's rocket attacks in populated areas (2). She says that these crimes "cannot compare" to the "criminality and lawlessness" of the Donbass republics, but she never justifies this. The killing of civilians, however intentional or unintentional, doesn't seem trivial, and it certainly can compare unfavourably to criminality and lawlessness. It's possible to invoke her logic for justifying Russia's invasion of Ukraine, citing the fact that Ukraine is a corrupt country that's controlled by oligarchs.
I'd rather have you than me as a judge.