We didnt need a humanitarian reason to fight Germany in 1939. Nobody did. Everyone was just too timid to reinstate hostilities and Hitler used that timidity to basically take over most of Europe without firing a single shot (if you don't count the thousands of political assassinations). Germany had violated the terms of the peace treaty which was still in effect.
When one side or the other violates the terms of a peace treaty, the peace is ended and any prior declaration of war would remain in effect. This is why our second entry into Iraq was perfectly legal. Hussein had violated the terms of the 1990 cease fire, so the Allies were free to reinstate hostilities. Unfortunately only Bush and Blair had the balls to enforce it.
We have never authorized military action in Libya and we have no compelling strategic interest in getting involved. For all we know, the rebels are worse than Khadaffi ever dreamed of being.
Exactly. And we pretend that somehow having France involved provides us some degree of separation. The French, iirc, were hated in western N. Africa. I assume that was sustained across N. Africa as well.