I'm opposed to U.S. intervention in Libya because I don't see it as necessary for U.S. interests, or necessary at all. France & Britain, which are gung-ho to act against Gaddafi, can easily turn the tide in favor of the rebels without U.S. assistance. But the UN resolution for intervention also sets a bad precedent that could harm U.S. interests in the future. The justification is based on protecting civilians. If you read the resolution, you will note that the words "to protect civilians" appear repeatedly.
If protecting civilians is a good justification for war, then it justifies any intervention in a foreign conflict. Civilians die in all modern wars. Sometimes they are targeted deliberately, but many times they are killed by accident. And sometimes they are killed because even though they are civilians, they are taking part in hostilities. Any government attempting to put down a rebellion has to kill civilians. Rebels usually don't have their own military, at least not in the initial stages. Armed rebels mingle with and hide amongst unarmed civilians. Even belligerents that care whether or not they kill civilians are going to have to kill some in order to fight at all. It should be obvious, since we have ongoing wars, that counterinsurgency operations require that some numbers of civilians die, no matter what extreme measures are taken to limit casualties.
Anti-American types at home and abroad are constantly condemning the U.S. for killing civilians in Afghanistan and Iraq. At some time in the future, will the U.S. face a U.N. led effort to intervene against us, justified by the supposed need to protect civilians? Is there the slightest doubt that the next time Israel has to launch a major military action there will be calls for international action to protect civilians?
What we are doing by signing on to this foolish UN resolution is handing our enemies a club to beat us with in the future. But as usual, our government never looks at the unintended consequences of its actions when it feels the urge to "do something."