Justice Department attorney Sharon Swingle made that assertion during a hearing about whether soldiers can be indefinitely detained, Courthouse News Service reported Tuesday.
Among the detainees who appealed to the three-judge panel of the D.C. Circuit is Hamidullah Khan, who was captured at age 14 and is still held at Bagram air base in Afghanistan five years later.
Judge Thomas Griffith said the only issue for the court was jurisdiction. Combatants held at Bagram are not within the jurisdiction of U.S. civilian courts.
John Connolly, an attorney for the detainees, told the panel that because of a lack of information from officials at Bagram, "we have no evidence that [Khan] was a child soldier."
The only thing Connolly said he knew for sure was that Khan "was a child."
International law says using a child under the age of 15 as a soldier is a war crime, the attorney said, so the United States can assert jurisdiction in Khan's case.
Swingle was skeptical about Khan's true age.
"Just to be clear, he is no longer a minor," she said.
She insisted Khan was being kept apart from adults at the prison and receiving an education.
Connolly said he had never heard that information.
In a final statement to the panel, Connolly said Khan was "not a homeless or stateless person," but someone with a "stable family" who "loves him."