In the case of Nicaragua in 1984, it went up the UN courts with the US being found to encourage human rights violations but it didn't amount to much since the US sits on the security council.
This is such a complicated topic that I really don't know whats the moral answer is. On one hand I don't believe we should be completely isolationist when there's so much going on in the world but on the other hand it's very easy to screw things up and impossible to predict the consequences. The best I hope for is having morally justified reasons for intervention rather than economically justified ones.
Lots of interesting stuff at the following links:
http://en.wikipedia.org/wiki/Covert_U.S._regime_change_actio...