The mounting likelihood of a campaign of vengeance by Moammar Gadhafi against his Libyan opponents makes the imposition of a no-fly zone an urgent matter.
The doctrine of the responsibility to protect applies to the Libyan civil war. The forces of Colonel Gadhafi - which seem to have recovered their effectiveness after the first shock of surprise at the opposition's uprising - have been engaging in aerial bombing of population centres such as Zawiya and Ras Lanuf, without any attempt to pinpoint their attacks so as to avoid and spare non-combatants.
The formation of an ad-hoc group of the world's powers to enforce a no-fly zone may be necessary, though a NATO plan would be better, preferably with the participation of regional powers such as Egypt. At present, Britain and France are the likely leaders. The European Union has already declined to act, particularly at the instance of the cautious German Chancellor, Angela Merkel.
Ideally, the United Nations Security Council would pass a resolution to this effect, but the outright opposition to any intervention on the part of Russia, a permanent member of the council, and the ambiguous reluctance of China make that highly improbable - at best, it would come too slowly to protect Libyan civilians.
A huge majority of the people of Libya live within 15 kilometres of the Mediterranean coast, which makes the establishment and maintenance of a no-fly zone considerably less difficult than it was in the former Yugoslavia and Iraq. Even so, the disabling of Col. Gadhafi's aerial defences may well be required.
At the same time, foreign boots on Libyan ground remain a highly undesirable complication. Indeed, the Libyan opposition's Interim Transitional National Council have explicitly excluded foreign ground troops from their request for intervention.
Hard as it is to obtain a clear picture of what is happening in Libya, enough is known about most of the ITNC's membership to refute the claims of Col. Gadhafi that the opposition leadership is an al-Qaeda front.
A no-fly zone may not achieve the end of the pathological Gadhafi regime, but it can prevent the reconquest of eastern Libya, and it could lead to a ceasefire. Above all, it holds the promise of saving many thousands of Libyan lives.