An African warlord with a $5 million bounty on his head unexpectedly fell into the lap of U.S. troops last week, presenting the Pentagon with a military victory but also a legal conundrum: what to do with the newfound prisoner?

Dominic Ongwen, a senior commander with the Lord’s Resistance Army, the brutal militia led by messianic leader Joseph Kony, surrendered to Muslim rebels in the Central African Republic. The rebels, in turn, handed over Ongwen on Jan. 5 to U.S. Special Forces who are advising African soldiers as they search for Kony in thick jungle terrain across four countries.

Since then, Ongwen has been sitting in U.S. military custody at a bush camp in the Central African Republic. Although U.S. officials and human rights groups have portrayed his surrender as a breakthrough in the hunt for Kony, the legal basis for keeping him in American detention is unclear.

Ongwen is not wanted on criminal charges in the United States. And while the Obama administration has authorized about 100 U.S. troops to help African forces look for Kony, their role is supposed to be limited to giving advice and sharing intelligence — not capturing or killing people.

In 2013, the State Department posted a $5 million bounty for information leading to Ongwen’s arrest or conviction. The justification for the reward was that Ongwen was wanted on war-crimes charges by the International Criminal Court, a judicial body based in The Hague that investigates mass atrocities. He is charged there with crimes against humanity for ordering massacres in Uganda.

An undated photo taken from the Interpol Web site shows senior Lord’s Resistance Army leader Dominic Ongwen. (Interpol/Via AFP/Getty Images)

On Tuesday, State Department spokeswoman Marie Harf said Ongwen would be handed over “soon” to an African Union military task force that has been searching for Kony and his fighters. The task force, which consists mostly of Ugandan soldiers who work alongside U.S. Special Forces, would then place Ongwen in the custody of the ICC to face trial.

The United States, however, is not a member of the tribunal, and many members of Congress are vigorously opposed to how it works. Moreover, the U.S. government in recent days has been at loggerheads with the ICC on another front, opposing efforts by the Palestinian Authority to join the court and extend its jurisdiction to the West Bank and Gaza Strip.

Sen. James M. Inhofe (R-Okla.), an advocate of the U.S. military mission to help destroy the Lord’s Resistance Army, applauded the apprehension of Ongwen but said it would be better for him to face justice in his home country of Uganda.

“The problem with the ICC is that it’s a black hole. Everybody disappears when they go there,” Inhofe said in an interview. “I don’t like the ICC, and I don’t like the way they operate. But we have a lot more important things to worry about than how the second-in-command of the LRA was taken out of existence.”

If Ongwen is taken to The Hague, “at least we won’t see him again,” Inhofe added.

Human rights groups disagreed, saying the ICC was set up specifically to prosecute people accused of atrocities and genocide. But they cautioned that Ongwen’s case remains fraught with complex legal questions.

For example, as someone who was kidnapped as a child by the LRA and forced to fight for Kony, Ongwen has dual legal status as both a victim and a perpetrator, said Daniel Bekele, Africa director for Human Rights Watch, an advocacy group.

U.S. defense officials have declined to elaborate on Ongwen’s detention or the legal basis for holding him. Under normal circumstances, he would be subject to the laws of the Central African Republic, which requires that he be given immediate access to a lawyer. But the country is so riven by turmoil that it lacks a functioning judiciary.

“It wasn’t something that anyone anticipated or was prepared for,” Bekele said. “Suddenly one of the most wanted men shows up, and it looks like it came as a surprise to all the stakeholders.”

Another unanswered question is who might get the $5 million reward. Rebel leaders with Seleka, a Muslim rebel movement in the Central African Republic, have said they captured Ongwen in battle and want the bounty for handing him over to the U.S. military.

The U.S. government has condemned Seleka in the past for killing civilians and bringing turmoil to the country, so it would be awkward for Washington to pay off the group.

Pentagon officials acknowledged that U.S. forces took custody of Ongwen from the rebels. But Army Col. Steve Warren, a Pentagon spokesman, said the LRA commander “surrendered,” implying that he turned himself in — a factor that would undermine the rebels’ claim to the reward money.

State Department officials, who manage the bounty program, declined to comment except to say any reward payments are kept confidential.