THE CAPTURE of Ahmed Abu Khatalla is a testament, as President Obama said, to the “courage and professionalism” of U.S. military, law enforcement and intelligence personnel. It vindicates Mr. Obama’s promise to stay focused, no matter how long it would take, on the hunt for the killers of Ambassador J. Christopher Stevens and three other Americans in Benghazi, Libya, in 2012. But this episode includes a couple of other lessons that Mr. Obama did not dwell on in his brief statement.

We believe the president is correct, Republican criticism notwithstanding, to send Mr. Khatalla to civilian court for trial. As Attorney General Eric H. Holder Jr. has said, the courts have proved their capacity to deal fairly and decisively with terrorism suspects. In one sense, to treat Mr. Khatalla as a prisoner of war and send him to the prison at Guantanamo Bay, Cuba, as the critics demand, would be to accord too much respect to his alleged behavior. And as Harvard law professor and former Bush administration official Jack Goldsmith pointed out on the Lawfare blog Tuesday, civilian courts are likely the only legal option for Mr. Khatalla’s detention; he is not covered by the congressional declaration that authorized the United States to go after the perpetrators of the 9/11 attacks.

It’s worth noting, however, that the Obama administration did not immediately read Mr. Khatalla his Miranda rights and clap him into a U.S. jail. Instead they put him on a ship where he could be questioned for intelligence purposes. This is the right call, but it also shows what Mr. Obama has been reluctant to acknowledge — that as long as the United States is engaged in hostilities with terrorists such as Mr. Khatalla, the criminal system alone is not sufficient. The country would be stronger if the administration worked with Congress to update the 2001 declaration and clarify the rules for interrogating such detainees.

In addition, dispatching U.S. Special Operations forces into other nations to essentially kidnap wanted men without their government’s permission is not the ideal method of law enforcement. The United States behaves this way when a country is unable or unwilling to assist in a legitimate apprehension. Libya certainly fits that description today, suffering as it does from feuding militias and a breakdown of law and order.

One reason the country finds itself in that sad state is that the United States and its allies, after conducting a bombing campaign that led to the downfall of dictator Moammar Gaddafi, didn’t stick around to help a new government establish itself. The United States can protect itself to a degree by killing (with drones) or arresting individual enemies. In the long run though, that will be a losing battle if it does not also work with partners to reduce the extent of lawless spaces where such enemies can be trained and sheltered.

President Barack Obama speaks about the capture of Libyan militant suspected of killing Americans in Benghazi. (Pablo Martinez Monsivais/AP)