NutLoose, it seems most of the locals want this. Not a shot was fired against the Russians. I even saw footage of local police walking past them.
At the end of the day considering how those people took power in Kiev, simply by taking it through force, they cannot really in moral terms say much to Russia now. Arguably Yanukovych could still be the legitimate President. If he were at some point in the coming days to formally request Russian military support Russia could say they are acting on behalf of the legitimate President who is asking for assistance! Then within the Ukraine it would come down to who backs who!
Then that is for the country to decide, similar to what is happening here with Scotland, not for a third party to march in and take control by force.
As for the legitimacy of the ousted a President, well it was their Parliament that voted him out, not the protestors, and they represent the electorate.