My first reaction to the UNSC resolution on Libya was surprise. I hadn't expected that a vote to authorize action would succeed, still less one that authorized action ("all necessary measures") far beyond merely enforcing a no-fly zone. That extra step seemed to come out of nowhere. It was vital. It may be what persuaded Libya to declare a ceasefire, and it gives Gaddafi reason to think about actually honoring it. The resolution, by the way, also allows troops on the ground, if it should come to that. It forbids an occupation force, a different thing.

To put it mildly, this is quite a moment for the UN, and for US relations with that institution. America has not led this drive to protect Libyan civilians. Britain and France can fairly claim to have done that. Read David Cameron's statement after the resolution passed. Impressive, I thought. There were three conditions for intervention, he explains: demonstrable need, regional support, and a clear legal basis--all now met.

So far, the US is just one partner. Could it remain as that--perhaps, as the Pentagon might prefer, even a junior partner--if the allies have to start shooting? That would be a very strange posture for the US: engaged in a military intervention that Washington is not directing. I wonder what the US public would make of it. Perhaps it is a sign of things to come: the difference that Obama makes; a US that goes along to get along; the kind of America the world thinks it wants, sometimes. Alternatively, it might be a formula for disaster. In any event, it's new.

For now, there's another problem. The resolution does not quite marry with the tone of British, French, and US officials talking as though they have taken sides with the rebels in their struggle against Gaddafi--a just cause, needless to say, if there ever was one. The resolution did not put the international community on the rebels' side in Libya's civil war. Emphasizing the protection of civilians, it called for a ceasefire, and the Libyan government has announced its compliance. Suppose this is genuine. Do we now police a partition that leaves Gaddafi in charge of most of the country? Or suppose it is a feint, the allies strike against the regime, and the struggle turns the rebels' way. What does protecting civilians require then? A rebel in a tank advancing on Tripoli is not a civilian.