“I fear this looks like a civil war”, one Libyan rebel commander from Misrata told the Associated Press, in the wake of a fierce firefight between rival militia factions using heavy weapons in broad daylight in Tripoli on Tuesday.  Four fighters were reportedly killed and five wounded in the clash ignited by the attempts of a Misrata-based militia to free a comrade detained by the Tripoli Military Council on suspicion of theft. But such clashes have become increasingly common in the Libyan capital over the past two months, as rival militias stake out turf in the power vacuum caused by the collapse of the Gaddafi regime. And while leaders on both sides of Tuesday’s clash were eventually able to broker a cease-fire, the deep fissures of tribe, region, ideology and sometimes even neighborhood that divide rival armed groups persist —and there’s no sign yet of the emergence of a central political authority with the military muscle to enforce its writ.

The residents and militias of Tripoli have been trying for months to persuade the Misrata and Zintan fighters who stormed the capital to topple the regime to go back to their home towns, but those fighters are staying put—and are accused of harassing the locals. They see themselves as the ones who shouldered the greatest burden in the battle to drive out Gaddafi, and they are suspicious of edicts by the National Transitional Council (NTC), which they see as self-appointed interlopers from Benghazi (the NTC’s recognition by the West and Arab governments as Libya’s legitimate government notwithstanding). The fighters of Zintan and Misrata are in no hurry to subordinate themselves to a national army led by returned exiles and a government of which they’re wary; nor are they willing to accept the authority of the Tripoli Military Council headed by the Islamist Abdel Hakim Belhadj, despite his endorsement by the NTC. Mindful of the political power that flows from being armed and organized, and determined to leverage that into a greater share of power and resources for the regions and towns they claim to represent, the regional militias are in no rush to give up their control of prized political real estate. They’ve ignored the Dec. 20 deadline to leave Tripoli. And, when NTC-backed armed groups tangle with them, as happened with the New Year’s Eve arrest of some of their men, they’re willing to fight.

“Freedom is messy”, former U.S. Defense Secretary Donald Rumsfeld famously offered as an explanation for the chaos that beset Baghdad in the weeks that followed the ouster of Saddam Hussein. The difference, of course, is that in Iraq, the U.S. military had established a monopoly of force —Rumsfeld was simply clinging to the hope that it wouldn’t have to be used to stabilize post-Saddam Iraq, and could be brought home pronto. But Libya, as we know, was a different kind of operation— an aproach hailed by U.S. and NATO officials as a new model of ‘intervention-lite’ in which Western powers and Arab allies could help indigenous populations oust odious dictators with minimal commitment of blood and treasure. While months of air strikes and a few hundred Qatari special forces troops on the ground proved to be enough to shatter Colonel Gaddafi’s regime, it could not—nor did it intend to—fill the resultant security void. NATO and its partners simply recognized the Benghazi-based NTC and its allied armed formations as the legitimate authority, supplied it with aid and resources, and hoped for the best.

The problem, of course, was that the Libyan rebels were never an army; they were patchwork of small local militia units, deserters from the regular army, and a smattering of former exiles with military experience. Moreover, the recognition extended by foreign powers to the NTC was far in advance of the extent to which Libyans, even many of those in the forefront of the battle to oust Gaddafi, were willing to accept its lead. The fact that the rebel leadership had not established an alternative power center meant that the collapse of Gaddafi also meant an effective collapse of state authority. The challenge now facing the rebels is to build a new state on the ruins of the old, and the first order of state-building business is establishing a monopoly on military force within its borders. The NTC is struggling to meet that challenge.

Residents of the capital complain of being menaced by the militiamen from out of town.  The situation is particularly grim for residents of towns and neighborhoods thought to have supported Gaddafi, which are routinely subject to abuse by fighters . The NTC may talk of “national reconciliation,” but it has precious little control over fighters whose actions imperil that objective. Instead, the NTC is forced to accommodate them.

Even as tribal and regional schisms intensify the sometimes violent contest among the different militia formations, the alienation of communities that had supported Gaddafi’s regime also creates fertile soil for an insurgency. There are certainly plenty of men of fighting age out there (many of them armed) who fought for the old regime. In some Tripoli neighborhoods, pro-Gaddafi graffiti still reportedly goes up nightly. And British officials warned late last month that a number of top al-Qaeda leaders have left Pakistan for Libya, looking to take advantage of the security vacuum to set up shop.

The security challenges would be more manageable if a political consensus existed on the terms for building a new democratic state in Libya, but that too remains elusive. The NTC has been beset with challenges over its less than transparent composition and process of selection—in December it even faced a tent-city protest established outside its headquarters to demand that it disclose its membership and make public its decisions. The Misrata and Zintan militias don’t trust the Benghazi rebel leadership, and they shamelessly use their military muscle to demand a greater share of the political pie—for example, refusing to hand over high-value detainees, such as Gaddafi’s son Saif al-Islam, until their political demands have been met. Last month, an umbrella group claiming to represent 70% of militia fighters demanded that the NTC granted them 40% of its seats.

The conflict among the militia is inherently political: It’s the form in which rival tribal and regional groupings are staking their claim to power and resources in the post-Gaddafi order. And it’s far from clear how the formal political system being put in place to regulate such competition will ease tensions. Yet, the criteria by which the NTC selects its own members has not been made public. And the draft law setting rules for elections to be held in June that the Council released for discussion last Monday suggests that the promise of elections may not resolve the emerging schisms. The draft evades the highly-charged issue of districting, meaning that there’s no clarity on how many seats in a new legislature will be allocated to each town and region, a decision that will shape the distribution of oil wealth in the new system. The draft law also plans to exclude as candidates those who hold positions in the current interim government and its local and military councils, officials of the former regime and those deemed to be late adopters of the revolutionary cause.

Thus the downside of intervention lite: It’s a lot easier to take down a regime, as the U.S. learned in Iraq, than it is to establish a new order. And yet in Libya, the forces trying to establish that new order are far weaker, in security terms, than the U.S. had been in Iraq, even if some of their leaders —most notably NTC President Mustafa Abul Jalil—enjoy the advantage of a legitimacy never accorded to the U.S. in Iraq. Given the mounting threat of chaos, Jalil’s authority may not be enough. Just as those Bush Administration Kool Aid merchants who insisted that most of the U.S. forces sent into Iraq could be brought home almost immediately suffered a nasty rebuke from reality, so might the advocates of Libya-style intervention-lite find themselves forced to reconsider their prescriptions in the months ahead.