As the violence in Libya intensifies and Libyan ruler Muammar Qaddafi increasingly turns to aerial assaults to stymie rebel advances, the question of whether the international community should impose a no-fly zone over the country has generated fierce debate. The tactic, which was used in Iraq and Bosnia in the 1990s, would prevent the Libyan Air Force from attacking civilians if effective but carries considerable diplomatic, military, and logistical risks.

Now, the Associated Press is reporting that Britain and France are drafting a United Nations resolution to establish a no-fly zone over Libya.The resolution would reportedly establish triggers for imposing a no-fly zone like the bombing of civilians or severe human rights violations. NATO is also assessing the viability of a no-fly zone and has begun around-the-clock aerial surveillance of Libya.

Libya's U.N. ambassador and opposition leaders have both called for a no-fly zone, but NATO members like Turkey and Germany oppose the measure, as do China ans Russia at the U.N. Security Council. In the U.S., Defense Secretary Robert Gates warned last week that imposing a no-fly zone would require a large-scale military operation and "an attack on Libya to destroy the air defenses"--which pundits like CNBC's John Carney argue is tantamount to declaring war. Yet Senators John McCain and John Kerry, both of whom support a no-fly zone, have questioned whether disabling Libyan air defenses would be necessary.

Why the difference of opinion? Reuters explains that the dimensions of a no-fly zone depend on its ambitions. For example, the international community could impose a no-fly zone without attacking Libya's air defenses, but it would put its planes at greater risk. Similarly, it could establish a no-fly zone over all of Libya or only over certain areas---rebel-controlled towns, for instance.

Reuters suggests that a no-fly zone would most likely be enforced by a "coalition led by the United States and Britain," but the Obama administration has said any military action in Libya must be an international effort.

While "Obama is believed to oppose U.S military intervention in Libya, partly because it could boost Qaddafi's standing," the Guardian observes, "if civilian deaths mount and the humanitarian crisis worsens, his hand may be forced. The U.S is also concerned that a golden chance to topple Qaddafi may be lost if the crisis is allowed to deteriorate into a low-intensity stalemate, with neither side able to best the other."