I suppose it depends upon what actions are taken.
Decrying is one thing, as was done recently in Honduras. Rolling the tanks in is something different, particularly when the US and the UK are signed up to a treaty promising to protect Ukrainian territorial integrity.
To be honest, I am not smitten with the new mob in power in Ukraine. I hope there's a proper election soon, and the Ukrainian people get to vote for who they want, but it should be pretty clear what is wrong with what Russia's doing.
Russia reportedly has the right to station 25,000 troops in Crimea. If they believe that an unruly mob has seized power it's not so unreasonable that they should wish to protect themselves by taking control of local military assets to prevent the new regime from using them.
I'm sure that there's similar precedent for the Western powers somewhere.
I too await elections but I'm worried that if the results don't turn out as desired, there'll just be another coup. the way it's been described here is that it's not just a case of ethnic Russians vs. ethnic Ukrainians there's also a working class Eastern Ukraine / middle class Western Ukraine dimension. A pro-Western government is not a given.