Syrian Democratic Forces soldiers rush through debris while a drone is heard above them in June. (Alice Martins/For The Washington Post)

A federal judge said Monday that she will rule shortly in a case in which she suggested the U.S. government is asking courts for a “blank check” to indefinitely detain American citizens held as enemy combatants in active war zones.

U.S. District Judge Tanya S. Chutkan of the District of Columbia stepped up concerns about an unidentified citizen and suspected member of the Islamic State detained as an enemy combatant for nearly three months without a charge after being captured in Syria and transferred to the U.S. military. The ACLU has petitioned to represent the man to assert his constitutional right to go to court to challenge being held in custody.

The U.S. government is seeking to throw out the ACLU’s case, arguing the government can secretly hold the man without court review for a to-be-determined “reasonable period” because no lawyer can establish legal standing to sue on behalf of the unnamed American.

“How on earth is the man to exercise his habeas rights,” and contest being held, Chutkan at one point asked attorneys for the government at an hour-long hearing. The judge said their position suggested “an end-run” around the Constitution by saying in effect “You don’t get to exercise your habeas rights until we decide what to do with you.”

ACLU attorney Jonathan Hafetz called the government’s position “Kafkaesque” and “a direct assault” on the authority established by the U.S. Supreme Court during George W. Bush’s presidency for U.S. citizens suspected of belonging to al-Qaeda and other terrorist groups after the Sept. 11, 2001, attacks to challenge detentions after being captured on the battlefield.

“The government’s claim that a federal judge does not even have the authority to determine if a U.S. citizen who has been imprisoned for nearly three months wants to challenge his detention is unprecedented, and completely unsupportable,” Hafetz said. “It not only strips citizens of a basic constitutional right, but it eliminates the important role of the federal courts as a check on actions by the president.”

Justice Department civil division attorney Kathryn L. Wyer said the decision of what to do with the detainee is temporary, “still underway, and the government is diligently attempting to reach that determination” but did not know how long it would take.

The Pentagon disclosed Nov. 30 — at Chutkan’s order — that the American had asserted his constitutional rights to a lawyer, halting law enforcement questioning. But the Pentagon stated in filings that it was “not currently aware” whether he wanted to challenge his detention in court.

Justice Department lawyers asked Chutkan to toss the ACLU’s habeas corpus petition on legal grounds, saying the group could show no relation to the man that would give it standing to sue on his behalf. As a result, the Justice Department argued, the court had no authority to weigh in on wartime detentions by the U.S. military in an overseas conflict zone.

Chutkan at an earlier hearing last month expressed incredulity at the “circularity” of that claim, saying it was the government that is withholding the man’s identity, preventing legal counsel from establishing contact with him or his family.

Wyer said there was no evidence the man wanted to challenge his detention, calling that “speculation.”

Chutkan appeared to reject that argument. “I don’t see it as at all speculative he wants to assert his rights,” the judge said Monday. “Are you saying an ordinary citizen and nonlawyer knows the difference between his Miranda rights and his habeas rights? He says he wants a lawyer, Isn’t that enough?”

Wyer replied, “He did not say he wanted to go to court . . . All he said was he didn’t want to answer questions without a lawyer present.”

The government has said the man surrendered in Syria to rebel Syrian Democratic Forces, and was turned over to the U.S. military on Sept. 14 and held since in military custody in Iraq. Wyer said the detainee has been visited by the International Committee of the Red Cross and could ask that group to contact his family to seek legal help. The government has said it is complying with the Geneva Conventions in not releasing his name.

Some national security law experts have said that there is agreement the executive branch does not have unreviewable discretion to indefinitely detain U.S. citizens captured on a battlefield, but that the military has some leeway to make a decision.

The key question is how long is too long, and who decides.

The U.S. Supreme Court in 2004 ruled U.S. citizens held as “enemy combatants” under war legislation are entitled to counsel and the right to challenge the evidence against them before a neutral arbiter.

But then-Justice Sandra Day O’Connor wrote in a controlling opinion that right does not attach at the initial capture but instead “only when the determination is made to continue to hold [him].”

U.S. 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.