NEW YORK — The American Civil Liberties Union sent a letter today to Defense Secretary Jim Mattis and Attorney General Jeff Sessions urging them to comply with the Constitution and ensure the legal rights of a U.S. citizen whom the military says was fighting on behalf of the Islamic State group in Syria.

The unidentified man has been held in U.S. military custody as an “enemy combatant” for approximately two weeks after being turned over by Syrian forces. He is reportedly being detained in Iraq.

“If the government has legitimate grounds to suspect the citizen fought with ISIS, he should immediately be transferred to the federal criminal justice system for criminal charges,” said the letter from ACLU Executive Director Anthony D. Romero. “The course you take with respect to the U.S. citizen in Defense Department custody is a critical test for this administration’s adherence to the rule of law.”

The International Committee of the Red Cross has said that the U.S. military is setting up a visit for officials to ensure that his treatment is in accord with the Geneva Conventions.

“As you no doubt are aware, indefinite military detention without charge has proven to be unlawful and illegitimate, resulting in prolonged (and ongoing) legal battles, human suffering, and the erosion of the United States’ moral standing in the world,” Romero wrote. “The detention of alleged ‘enemy combatants’ at Guantánamo, for example, has violated human rights guarantees, resulted in widespread international condemnation, and created a still-existing category of ‘forever’ prisoners that is an affront to fundamental constitutional and international law norms.”

Since 9/11, federal courts have convicted more than 620 people on terrorism-related charges.

The full letter is here:

https://www.aclu.org/letter/aclu-letter-trump-administration-detained-american-suspected-fighting-isis