The UN resolution authorises "all necessary measures" to protect civilians under threat of attack - short of an occupying force.

BBC: Cameron: Libya UN resolution makes mission 'difficult'

Returning to the fields after years spent in Cambodia as part of Vietnam's occupying force, many face unemployment and rejection.

ECONOMIST: Vietnam

But under international law, occupation begins when territory is actually placed under the authority of an occupying force, according to the Pentagon.

CNN: Coalition to assert authority in Iraq

"Arab forces cannot be part of an occupying force, " Moussa said.

CNN: Arab leaders pledge reform on their terms

It is not difficult to imagine a situation where there is extended Libyan resistance to the occupying force followed by international condemnation of the counterinsurgency effort.

FORBES: How A Libyan No-Fly Zone Could Backfire

It is not clear if the proclamation will have any legal implications for U.S. forces -- specifically whether they would become the declared occupying force of Iraq under the Geneva Conventions and other international laws.

CNN: Coalition to assert authority in Iraq