Washington (CNN)The legal battle over the detention of a US citizen accused of fighting for ISIS entered a significant new phase Friday as his attorneys submitted a filing that experts say could set up a showdown over the legal underpinning of today's war on terror.
ACLU challenge in case of American detained as ISIS fighter targets 9/11 law
The case of the unnamed American held as an enemy combatant in US military custody in Iraq has moved quietly over a series of procedural hurdles since he was turned over to US forces by an American-backed militia in Syria last September.
Now, after successfully inserting itself as a representative for "John Doe" and securing an order from a DC federal judge that would prevent his immediate transfer to a third country, the American Civil Liberties Union argued Friday that the US government acted illegally by detaining the man, potentially setting up a major test of the controversial post-9/11 Authorization for Use of Military Force.
"For nearly five months, the government has been detaining an American citizen without charge or trial, based on legal theories that no court has ever endorsed," the ACLU wrote in its filing.
At issue is whether the government can use the military force statute -- signed into law in the days following the terrorist attacks of September 11, 2001, and granting the US president the power to target those responsible for the attacks -- to detain an individual accused of fighting for ISIS.
Under the law, the president can use force against "those nations, organizations, or persons he determines planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001 or harbored such organizations or persons." The US has blamed al Qaeda for the attacks, and the group's late leader, Osama bin Laden, claimed responsibility for them.
"The answers to these questions are not clear, and if I were the government I would not want to risk litigating them," said Matthew Waxman, a professor at Columbia Law School and former Pentagon adviser on detainee issues.
The Authorization for Use of Military Force has been debated and reinterpreted over the years to match a changing enemy, but despite scrutiny it has avoided a significant challenge in Congress or the courts and remains the basis of the ongoing fight against ISIS, a group that originally called itself al Qaeda in Iraq.
Friday's court filing could represent the first serious challenge to the law.
In an interview before the ACLU filing, a Justice Department official said there were a "variety of possibilities" under which the government believes it can detain Doe, including the 2001 Authorization for Use of Military Force, a second such authorization signed in 2002 that provided the legal basis for the Iraq War and the president's war powers under Article 2 of the Constitution.
"We are very confident that we have a strong legal and factual basis to detain this person as an enemy combatant and are fully prepared to defend our authority to do that if that's what ends up being our decision about what the best outcome is for this guy," the official said.
The ACLU also provides in the filing the first public account of the detainee's story, writing that he "sought to understand firsthand and report about the conflict in Syria" and "was kidnapped and imprisoned by ISIS" and "tried numerous times to escape."
"Not even the government alleges that he ever took up arms against the United States or anyone else," the ACLU writes.
In its filing, the ACLU also rebuts the government's defense of the detention under the 2002 Authorization for Use of Military Force and the president's constitutional powers.
In a briefing schedule, the federal judge presiding in the case allows for the Justice Department to submit a further response to the ACLU's Friday filing.
The government could also bring criminal charges against Doe, a dual Saudi national, in US civilian court, or, as it has floated in previous hearings, attempt to transfer his custody to a third country.
If Judge Tanya Chutkan does, however, eventually rule in favor of the ACLU's petition against Doe's detention, she could open the door to a greater challenge to the use of the Authorization for Use of Military Force in the global war on terror, Waxman said.
"Detaining an American citizen fighting for ISIS in Syria puts this whole controversial argument about the AUMF before a court, because he has a right of habeas corpus to challenge his detention," Waxman said.
"If the government were to lose this argument, the detention case would call into question the entire legal framework of counter-ISIS operations," he said.