everything i've seen suggests to me that the russians were legitimately concerned about being evicted from their naval base, and that they concluded that the only way to ensure that wouldn't happen would be to annex the region. might the new ukrainian government have allowed them to stay? maybe. but, given their nationalist (and anti-russian) rhetoric and their projected alliances, the russians seem to have calculated this was too risky to allow to happen organically. the rest is propaganda.
i really think it's as simple as that. i don't consider this situation to be at all complex. the russians are simply asserting control over a naval base that they feel was threatened by events in ukraine. that is all.
i'm still irked by the lack of transparency, and not really happy about the annexation, but i can reasonably understand that through the policy not yet being entirely formed. if the goal is to maintain control of the port, is this the most reasonable approach? it certainly is. is there much of a difference between setting up an autonomous region as a protectorate and just annexing it? merely legally.
i do agree with the prof, though, in his view that russia is making it seem like everything follows the law perfectly well. let us recall that the bush administration made sort of a big deal about american sovereignty giving it the right to act unilaterally, outside of the united nations. iraq was completely illegal. obama has softened this, but not retreated from it. consider libya, which was basically a trick (the resolution was to protect civilians in the case of attacks by ghadaffi, but nato used it to invade without demonstrating that such things were happening). so, this seems to be a systemic shift in american policy, one that would give a certain OLD right strain a nice big smile: fuck the pinkos at the un, the americans can do what they want. so said mr. birch to mrs. roosevelt...
the russians have been reacting to this by upholding international law at every opportunity they can. do they really believe what they're saying? well, maybe they've convinced themselves. but, it's mostly been a way to try and rein in american hegemony. and, what else can they do? they can no longer threaten the americans. so, if the question is "or else what?" then the russian response is "or else you're in breach of international law and will be condemned by the international community."
weak? an understatement, but it's what they've got. so, they've been sort of obsessed with it. it's become very routine for the russians to try and follow international law as best they can to set that example.
that doesn't mean they believe in it. "niceties" is the right language. and they'll likely keep it up.