With no credible national army — and the dispersal of the big militias that had sometimes acted in its place — the central government has had little coercive power to push back. Mr. Zeidan has issued repeated deadlines and ultimatums that have passed without consequence. (And Mr. Jathran has further humiliated him by appearing on television with $20 million in government checks he said had been offered under the table to restart the oil.)

Government officials have, in fact, empowered the tribes around the country by turning to tribal elders to resolve the blockades. In the case of Mr. Jathran’s blockade, the locally powerful Al Magharba tribe said it had mediated a deal to reopen the ports by last weekend. But Mr. Jathran said in a statement online that he was still holding out until all of his demands were met.

“They are talking to tribal leaders and ‘wise men!’ ” Husni Bey, Libya’s most prominent business mogul, scoffed in an interview. “This is a farce, like they are still thinking they will sit under a tent and decide and talk and have nice kisses on the cheeks and their problems will be swept under the carpet.”

Colonel Qaddafi was a master of such tactics. After abandoning his own early, nationalist attempt to eradicate Libyan tribalism, he switched to cultivating tribal loyalties and pitting tribes against one another. His aim was to prop up his own authority without building the national institutions that might have constrained his peculiar personal power. His ouster promised a more transparent and democratic order, but it also opened a new scramble for advantage among cities, tribes and even Tripoli neighborhoods, as well as Islamist groups.

In Tripoli, the militias began disappearing from the streets after Nov. 15, when a protest outside the base of a militia from the city of Misurata escalated into a shootout that killed 46 civilians, according to a count by Human Rights Watch.

It was in a sense the latest turn in a historic rivalry between the citizens of the capital and the tribes of Misurata. But citywide outrage forced some Misuratans to retreat to their hometown and made others newly responsive to the government. “Now no one is actually saying, ‘No, we aren’t going to give up our arms or leave those places,’ ” said Mr. Mihirig, the minister in charge of their removal.

But Misuratans and militias in Tripoli did not give up their weapons; they only relocated, with some moving underground within Tripoli. The many small neighborhood “brigades” that formed in Tripoli after Colonel Qaddafi fell — armed gangs, really — were a bigger problem, Mr. Mihirig said, calling the smaller, less visible local militias armed “interest groups” led by “warlords.”