FORT MEADE, Md. — Khalid Sheikh Mohammed, the self-described architect of the Sept. 11, 2001, terrorist attacks, and two men accused of being co-conspirators were absent from a military commission hearing Tuesday as a military judge took up a dispute over whether the defendants will be permitted to wear camouflage clothing to the courtroom at Guantanamo Bay, Cuba.

An official with the legal staff for the prison operation, whose name was not disclosed for security reasons, testified that she had informed each of the five defendants of their right not to come to court Tuesday morning. Two — Mohammed’s nephew Ali Abd al Aziz Ali and Mustafa Ahmed al Hawsawi — chose not to leave the detention facility.

By contrast, Mohammed decided to come and was taken to a holding cell outside the high-security courtroom facility. But he then decided just before the session began to remain in his holding cell and watch via a closed-circuit feed, the official said.

The other two defendants, Ramzi bin al Shibh and Walid bin Attash, attended court and sat quietly. As they did Monday, both wore traditional loose white clothing, vests and turbans.

Clothing dominated the morning session, which was watched by reporters at the base and was also shown at several U.S. viewing centers, including at Fort Meade.

Defense lawyers asked the judge, Col. James L. Pohl of the Army, to order the commander of the prison camp to allow the men to wear camouflage vests while they are inside the courtroom. The prison commander had prohibited the vests, saying that they were inappropriate courtroom attire and that they raised a security issue because they have pockets.

But Capt. Jason Wright, who is representing Mohammed, and Maj. William Hennessey, who is representing bin Attash, contended that it would undermine their clients’ defense to refuse to let them wear such clothing.

The defendants are accused of being unlawful combatants, meaning they do not get the same legal immunities as regular soldiers under the laws of war. One important factor in making someone a lawful combatant is that he wears clothing that distinguishes himself from a civilian.

The lawyers said that refusing to let their clients wear military-style clothing would help prosecutors make that case.

Wright also said that Mohammed had worn a camouflage vest while fighting the Soviets in Afghanistan and had offered to remove or sew shut any pockets on the vest.

The lawyers also noted that a defendant in a separate military commission case, Majid Khan, had been allowed to wear a Western-style suit with pockets to court, saying it would be arbitrary to deny their clients pockets.

A prosecutor, Maj. Joshua Kirk, argued that the military commander had “inherent authority” to prevent detainees from wearing inappropriate clothing, but he conceded that it was up to Pohl to decide what defendants could wear in the courtroom.

The judge also questioned whether the government had a real standard or was just blocking whatever the prison commander did not like, and he pressed the prosecution to explain why it was worth fighting over.

“We’re spending an hour talking about how they are dressing for court,” he said. “I mean, who really cares? I don’t mean to make light of it. They care. But you’re the one objecting to it.”

Pohl ruled that the detainees could wear anything they wanted — including “generic” camouflage vests — with three exceptions: official Guantanamo prison garb of a different color than their current security status, any U.S. military uniform or part of one, or anything else that a representative of the prison commander can testify as to why it would pose “legitimate security concerns.”

In May, during a chaotic arraignment hearing, defense lawyers said one reason their clients were unruly was that they had been prevented from wearing clothing that they had brought for them. Several lawyers for other defendants indicated that the prison task force had since relaxed the rules, allowing them to wear vests and turbans but still ruling out camouflage.

The pretrial motions hearing began Monday with all five defendants acting far more cooperatively with Pohl than they had at their arraignment. About two dozen motions are on the docket, and the hearing is expected to last through the week.