No one did or can 'give' us the right, we claimed the right to take action because we could, and because it was in our economic and political interests to do so. Call me cynical, but this is the nature of nationhood, and you see this scenario repeated in different places and times featuring different players throughout history. We need no other motive beyond 'it is in our interests to do this' to do something, and we certainly aren't required to seek permission from the U.N. or anyone else to do it.

Note that I am not defending the rightness or wrongness of these particular actions, and I have no interest in getting into another Iraq flamewar. I'm just answering that 'who gives you the right?' question honestly.