Before any state resorts to the use of force in Libya or anywhere else, it needs to answer a series of pragmatic and ethical questions, even if the legal hurdles are cleared through a United Nations Security Council resolution authorizing intervention.
In terms of just war theory, the basic principles are neither new nor uncommon. They are derived loosely from the Christian just war tradition and more recently adapted in the Responsibility to Protect Doctrine (R2P), which abridges state sovereignty and the inviolability of borders in favor of protecting populations from barbarous governments.
Both sovereignty and territorial inviolability are codified in the U.N. Charter, and during the Cold War each received strong and widespread support. After the Cold War ended in 1991, and especially after the famine in Somalia (1992-3), genocide in Rwanda (1994) and ethnic cleansing in Kosovo (1998-9), concern for human rights has increasingly come to trump sovereignty in states whose governments deliberately neglect or abuse a subset of their own citizens. R2P, for example, seems to have been on Obama's mind when, in his speech last Wednesday night, he declared, "When our interests and values are at stake, we have a responsibility to act."
Four principles of just war theory and R2P must be answered prior to undertaking a justified resort to arms.
First, are the intentions behind the action proper? Is one fighting to protect others, or is one fighting to protect one's narrow interests? Or both?
In the case of Libya, the question has been posed and answered on humanitarian grounds. President Obama clearly articulated the U.S. position, albeit a bit late in the game: to prevent the massacre of Libyan citizens. Given the past four decades' history of Qaddafi's treatment of his citizens, Qaddafi's threat that he was about to kill large numbers of his own citizens was a credible one. Intervening to prevent a credible threat of this sort would be just.
Second, is force a last resort? Qaddafi's opponents were virtually unarmed and even more poorly led than Libya's military. After some initial surprise and a few defections, Qaddafi's forces rallied and rapidly brought heavy firepower to bear on the resistance. The result was the rapid collapse of organized resistance and the imminent threat of mass killing. Force of some sort seemed the only way possible, given the time pressure, to respond.
Third, are the means to be employed proportional to the political objective? The answer to this question is murkier than the first two. This became apparent when the coalition air power targets expanded beyond protecting the population to include Qaddafi's personal compound and military assets throughout the country.
The escalation calls the true political objective into question. Is it to deter Qaddafi and Libya's military from the mass murder of civilians? Or is it to cause sufficient damage to Qaddafi's armed forces, his chief support in an illegitimate dictatorship, so that his own soldiers turn against him or he grudgingly departs? It is not clear that either a no-fly zone or an escalated target set will produce either political objective. Military means that might do so include arming the rebels (not workable since they possess insufficient skill to use the arms) or -- and here's the problem -- inserting U.S. or allied combat forces.
This leads to the final question, and this is the question that should have stopped the intervention in the first place: Are there reasonable prospects for success? Or might the use of force produce more harm than good?
The best prospects for success come in one of the military's traditional blind spots: the signaling power of force. Psychologically speaking, if a significant minority of Qaddafi's supporters believe he will ultimately lose, they will defect, making his exit (either on a plane or in a box) a reality. So long as they believe the international community's resolve will weaken and the rebels will falter, they will continue to support Qaddafi and he will remain in power.
Neither side now seems sure, which is one reason why Libya's new civil war is in a stalemate. The difficulty is that as in all strategic interactions, Qaddafi's forces are already adapting to the new tactical and operational reality, and they are adapting faster and better than the rebels.
The U.S. and its allies, for their part, have been shoved into a dilemma: If they do not escalate, the rebels will falter and Qaddafi will extract his revenge, ultimately inflicting what the U.S.-led coalition originally intervened to prevent (torture and murder). If they do escalate, they risk shattering their coalition and provoking an Arab-Islamic backlash against "western imperialists and crusaders," knocking the legitimacy prop from beneath the rebels and causing jihadis around the globe to pack their bags for Libya.
Like Operation Restore Hope, the well-intended but ill-fated humanitarian effort to save Somalis from themselves in 1993, each seemingly isolated political objective is in fact connected to a broader objective that cannot be engaged without counterproductive consequences. It seems that we face a similar situation: not intervening is intolerable, but successful intervention appears elusive.