Troops with the Syrian Democratic Forces drive on June 7 into the Mishlab district of Raqqa, the former capital of the Islamic State in Syria. (Alice Martins for The Washington Post)

The Defense Department confirmed Thursday in response to a federal judge’s order that an unidentified American citizen and suspected member of the Islamic State detained for 2½ months without charge as an “enemy combatant” in Syria has asserted his constitutional rights to a lawyer. But the government said it did not know whether he wants to go before a court.

The disclosures came after Justice Department lawyers unsuccessfully argued in a contentious, hour-long hearing Thursday morning before U.S. District Judge Tanya S. Chutkan that the court lacked authority to oversee U.S. military operations in an overseas conflict zone.

Chutkan’s demand for information marked a potential first step toward determining whether the ACLU or private counsel may represent the detainee, whom the government has said was captured in Syria, turned over to the U.S. military Sept. 14 and moved to a temporary detention facility in Iraq.

The ACLU suit filed on the man’s behalf threatened to reignite court battles fought during the George W. Bush administration, when the Supreme Court ruled that U.S. citizens cannot be held indefinitely as members of al-Qaeda or other terrorist groups under war legislation Congress passed after the Sept. 11, 2001, attacks. The court ruled that they are entitled to counsel and the right to challenge the evidence against them before a neutral arbitrator.

“This is the exceptional circumstance. This is the nightmare scenario,” ACLU attorney Jonathan Hafetz argued in court, describing as a constitutional “black hole” what he called the government’s assertion of unchecked power to indefinitely detain a U.S. citizen without charges, a lawyer or court review.

After the filing, he said the detainee’s request for an attorney reinforced the group’s demand that the man be given access to counsel, adding, “The Trump administration’s position that it can lock up an American in secret without charges or the ability to challenge the detention in court is not how our legal system works.”

Justice Department civil-division attorney Kathryn L. Wyer told the court that the U.S. military had permitted the man visits by the International Committee of the Red Cross, complied with Geneva conventions in not releasing his name, and acted under U.S. case law establishing its authority to hold wartime detainees for a preliminary and “reasonable period” to decide their final disposition.

The Justice Department asked Chutkan to toss out the ACLU lawsuit on legal grounds, saying the organization lacked standing to file a challenge as a “next friend” of the American to inform him of his rights and give him the chance to have legal representation. The ACLU filed a habeas corpus petition on the man’s behalf to require the government to justify his detention without charges.

Wyer argued unsuccessfully that Chutkan lacked jurisdiction to hear the matter, because the ACLU was “a stranger” to the American, had never met with him and had no right to claim to represent him.

Wyer warned of “far-reaching consequences whenever U.S. forces detain an individual while engaged in active military operations in a foreign country” if the court ruled that any third party could sue on the detainee’s behalf in U.S. courts. The government argued that the American may have asked the Red Cross to contact his family, which could be seeking a lawyer to represent him.

Chutkan expressed incredulity at “the circular reasoning” of the government’s stance, saying that it was withholding the identity of the man, then opposing the ACLU’s attempt to go to court in his behalf because it did not know him.

Chutkan, a 2014 appointee of President Barack Obama and a District assistant public defender early in her career, said she intended to rule “expeditiously” on whether the court can take steps to get the detainee counsel or find out whether he wants to appear in a court.

The Washington Post reported last month that Justice Department officials did not think it had enough evidence to charge the man, who was questioned first by an interagency interrogation team for intelligence purposes and then by an FBI team seeking enough admissible evidence to bring a case against him. The man refused to talk and demanded a lawyer, the officials said.

In a filing to meet a 5 p.m. Thursday deadline, Wyer confirmed that during the law enforcement questioning, the man was informed of his rights and “stated that since he was in a new phase, he felt he should have an attorney present.” Told “it was unknown when he would be able to have an attorney,” the man said “that it was ok and that he is a patient man,” Wyer added in the filing.

No further law enforcement questioning has taken place, and the man made clear in a later request to speak with an interrogator that he did not wish to speak to FBI agents, Wyer said.

She added, “Respondent is not currently aware of any additional information regarding the individual’s wishes in connection with his invocation of constitutional rights or pursuit of remedies in U.S. courts.”

A Defense Department spokesman, Air Force Maj. Ben Sakrisson, said last month that the government continues to withhold the detainee’s identity and circumstances because “there are still a number of U.S. agencies looking at the circumstances of how he came to be detained” and what should happen to him now.

Wyer said the process is temporary, “still underway, and the government is diligently attempting to reach that determination” but did not know how long it would take.

Chutkan called that position, “Trust us, we know what we’re doing.”

“That scenario, that kind of unchecked power, is, quite frankly, frightening,” she said.

Officials told The Post that the man once had ties to the Pacific Northwest but that most of his family and roots are in the Middle East. National security analysts said the United States could negotiate with the man’s family and country of second citizenship to accept his return under conditions that he be monitored and not be allowed to travel.

Or, they said, he could be turned over to Iraqi authorities for trial. But conviction would still require evidence, and it is against U.S. law to send prisoners to a country where they could face torture, which Human Rights Watch says is rampant in Iraq. He also could be sent to the U.S. detention facility at Guantanamo Bay, Cuba, which would invite immediate litigation.