WASHINGTON — The American Civil Liberties Union told a federal court today that the Trump administration has no legal authority to detain an American who has been held by the U.S. military in Iraq for nearly five months without charge.

The U.S. citizen has been detained as an “enemy combatant” for allegedly being an ISIS fighter, an accusation denied in a brief filed today in the habeas corpus case challenging the detention.

The government has claimed that it can detain the citizen under the 2001 Authorization for Use of Military Force (AUMF) passed by Congress shortly after the 9/11 attacks, the 2002 congressional authorization for the Iraq War, and unilateral presidential power to imprison Americans indefinitely for national security purposes.

“The executive cannot circumvent Congress by imprisoning Americans based on statutes authorizing military force for different wars against different adversaries,” said ACLU attorney Jonathan Hafetz. “In detaining this U.S. citizen without charge for months on end, the Trump administration is unlawfully reviving one of the most egregious abuses of executive power we saw after 9/11. The administration is also pushing the dangerous claim that President Trump has the independent authority to indefinitely detain Americans at will.”

The 2001 AUMF authorized the military to capture and detain people who were part of or supported al-Qaida and the Taliban and engaged in hostilities against the U.S. or its allies. The ACLU’s brief argues that the 2001 AUMF cannot be used to cover ISIS because it did not exist in 2001 and is openly at war with al-Qaida. The Supreme Court has only upheld the military’s power to detain a U.S. citizen under the 2001 AUMF in a case where a man was captured while fighting alongside Taliban forces in Afghanistan.

Today’s brief is here:

https://www.aclu.org/legal-document/doe-v-mattis-aclu-response-governments-factual-return

More analysis from the ACLU on this issue is here:

https://www.aclu.org/blog/why-us-war-isis-illegal