It seems likely that there will have to be some kind of post-conflict force in Libya. Western leaders have said that they won't send ground troops. That's no doubt true for the combat phase. But what about after most fighting ends or when Gaddafi and the rebels strike a deal? Unless rebel forces win decisively and quickly establish a functioning government, some kind of international support will be necessary to stabilize the country, as was the case in Kosovo and Afghanistan. What's more, if the rebels do not prevail throughout the country, a buffer force between rebel and Gaddafi-controlled areas may be necessary. Some early thoughts on options:

A NATO-led stabilization force, akin to the International Security Assistance Force (ISAF) in Afghanistan. An ISAF-like force would have the advantage of superior firepower and resources and would presumably be able to deter outbreaks of fighting. But it could easily be portrayed as  a Western occupation force, which the UN resolution specifically warned against and which Arab states have rejected. Plus, NATO's having trouble enough getting its members to cough up troops for Afghanistan. How many will have the appetite for a Libyan excursion? 

An ad hoc international force with a UN mandate. At the moment, this may be the most likely option. It allows those countries willing to contribute to do so, without having to get the stamp of a regional organization, which could be tough. The downside is that an ad hoc force wil not have a ready-made command structure. Ad hocery was tried in Afghanistan after the fall of the Taliban. It didn't work particularly well, and NATO took over operations in August 2003.

A force under the control of the Arab League or the African Union. The African Union has taken on peacekeeping operations in Sudan and Somalia. Reviews are very mixed. The Arab League played a critical role in legitimizing the current intervention. But would either be credible or competent as the organizer a post-conflict stabilization force? 

A UN peacekeeping force. The blue helmets could be an option and would have the advantage of representing the international community rather than any particular region. But UN peacekeeping forces are best in static situations and generally less effective when force may be required (see Sudan, Congo, Cote d'Ivoire). UN peacekeepers could be a good option as a buffer force if there is a clear division of the country between rebels and Gaddafi forces.