Not really, there's a remarkable amount of evidence for their intervention in Crimea. Even a decision to occupy eastern border towns wouldn't really be a massive problem since Ukraine's sovereignty is up in the air at the moment given that Crimea voted for independence. No way in hell is the UN going to get involved in any way other than sanctions, and if anything the US is even less enamored of the idea. Maybe the UN could intervene effectively in a small country with a tiny insurgency, flat terrain, friendly countries on the border and a vastly sympathetic population, but using force to dissuade separatism in Ukraine is a bad idea considering Russia's oil resources and the fact that it's got one of the most powerful militaries in the world. The Russian authorities been remarkably prudent in conducting all this.