Lindh, captured in 2001, is among dozens of prisoners captured in Iraq and Afghanistan by US forces and convicted of terrorism-related crimes following the September 11, 2001 attacks.
John Walker Lindh, the American captured in 2001 fighting for the Taliban, has been released early from federal prison on Thursday. However, some US lawmakers fear he remains a security risk.
Now 38, Lindh is among dozens of prisoners captured in Iraq and Afghanistan by US forces and convicted of terrorism-related crimes following the September 11, 2001 attacks.
His release brought objections from elected officials who asked why Lindh was being freed early and what training parole officers had to spot radicalisation and recidivism among former militants.
Leaked US government documents published by Foreign Policy magazine show the federal government as recently as 2016 described Lindh as holding "extremist views."
"What is the current interagency policy, strategy, and process for ensuring that terrorist/extremist offenders successfully reintegrate into society?" asked US Senators Richard Shelby and Margaret Hassan in a letter to the Federal Bureau of Prisons.
Lindh's parents Marilyn Walker and Frank Lindh did not immediately respond to requests for comment. Lindh's lawyer Bill Cummings declined to comment.