“In many ways, he’s a case study of a larger issue they have in government: They arrested hundreds of people since 2002 but there’s not a system in place to address these individuals,” Mr. Hughes said.

In all, 346 people have been charged and convicted of jihadist terrorism related crimes since the 2001 terrorist attacks, according to David Sterman, an analyst at New America who studies terrorism and violent extremism, citing a database maintained by the research organization. About one-fourth of those prisoners, 88, have been released, he said. About half should be released by the end of 2025, with 19 of them, including Mr. Lindh, on the path for release this year and next, Mr. Sterman said.

Mr. Hughes earlier worked on how to counter violent extremism in his capacity as a staff member at the National Counterterrorism Center, which was established in response to the 2001 terrorist attacks. So far, however, he said, the Bureau of Prisons, Justice Department, F.B.I. and court probation offices have yet to develop a single strategy for helping former jihadists re-enter society.

Because of the vacuum, he said, the best hope for Mr. Lindh is that his probation officer finds a Muslim former federal prisoner — someone who has conservative beliefs but is not radical — to help him navigate society.

“Ideally, you’d team him up with a mentor, somebody who perhaps had the same experiences as he may have had and came out the other side better of because of it,” Mr. Hughes said.

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Johnny Spann, the father of the C.I.A. operative who was killed in Afghanistan, remains bitter about the Lindh case and said he is distrustful of the decision to let Mr. Lindh go. His son is buried at Arlington National Cemetery, about eight miles from the Alexandria courthouse where Mr. Lindh was charged.

“We’ve got a traitor that was given 20 years and I can’t do anything about it,” said Mr. Spann, a real estate dealer in Winfield, Ala. “He was given a 20-year sentence when it should’ve been life in prison.”