Three Sept. 11 defendants took a judge up on his offer to let them skip their military tribunal Tuesday and the proceedings went on without them. The Guantanamo detainees won a new request to return to court in camouflage clothing if they wanted.

Khalid Sheikh Mohammed, the self-professed 9/11 mastermind, was not in the courtroom while attorneys delved into a dense debate on legal motions, including rules for handling classified evidence at trial and what kind of clothing would be allowed.

Only two of the five defendants made it to court for the second day of the weeklong hearing. Mohammed, Saudi defendant Mustafa Ahmad al-Hawsawi and Pakistani national Ali Abd al-Aziz Ali — Mohammed's nephew — all stayed away.

The presiding judge, Army Col. James Pohl, ruled Monday that the defendants didn't have to attend the hearing every day this week, although he said they would have to attend their formal trial and may need to attend future hearings.

Mohammed was taken from his cell at the U.S. base in Cuba to a holding cell outside the courtroom, then chose to boycott at the last minute, said a Navy officer whose name was not released by the court for security reasons.

The 47-year-old Mohammed, who has previously said he conceived and orchestrated the Sept. 11 attacks, gave no reason for sitting out the hearing. But on Monday, he dismissed the military tribunal with scorn, saying "I don't think there is any justice in this court."

Authorities have portrayed the other defendants as Mohammed's underlings, who provided logistical and other help to the Sept. 11 hijackers. All five face the same charges, which include terrorism and murder, in what is considered one of the most significant terror prosecutions in U.S. history. They all could get the death penalty if convicted at a trial that is at least a year away.

Al-Hawsawi and al-Aziz Ali didn't provide any reason for their absence, but a lawyer for al-Aziz Ali had said on Monday that his client's father had recently died in Kuwait and he was grieving for him.

In attendance were Walid bin Attash, a Yemeni who grew up in Saudi Arabia, and Ramzi Binalshibh, another Yemeni who was originally chosen to be one of the hijackers but couldn't get a U.S. visa to enter the country. Both sat through the hearing without incident, apparently following the proceedings.

Prosecutors had argued the rules for the special wartime tribunals known as military commissions require defendants to attend all court sessions, and said the defendants' presence would ensure the proceedings are legitimate. But lawyers for the men said the threat of forcible removal from their cells would be psychologically damaging for men who had been brutalized while held by the CIA in secret overseas prisons before being taken to Guantanamo in September 2006.

The judge granted another concession to the defendants Tuesday, giving them more freedom to choose what they wear in court.

Mohammed and bin Attash had wanted to wear camouflage clothing in the courtroom at their May arraignment, apparently to portray themselves as soldiers, but the prison commander refused to allow it. The judge ruled they could wear some camouflage items as long as they were not U.S. military uniforms.

Mohammed wants to dress like a "prisoner of war," said his lawyer, Army Capt. Jason Wright, and should be allowed to "wear the same type of uniform he wore while fighting for the U.S.-supported Mujahedeen in Afghanistan and in Bosnia," he said.

Defense lawyers have said that the clothing restrictions had been a factor that led to their protest at their May arraignment, when the men ignored the judge's questions and wouldn't use the court's translation system. This week, the men have all appeared in traditional loose fitting traditional tunics, vests and hats that they chose to wear.

The judge also began hearing arguments Tuesday on a protective order, a set of rules for handling classified evidence that the defense and other critics say are overly broad.

Protective orders are standard in civilian and military trials, and prosecutors say the one proposed for the Sept. 11 trial is necessary to prevent the release of classified secrets and protect national security.

But defense lawyers say the rule would make it harder for them to introduce the men's own accounts of the conditions of their captivity during the several years they each spent in CIA-run overseas prisons, where they were subjected to what the government calls "enhanced interrogation techniques" that included being tied up in uncomfortable "stress positions," forced nudity, sleep deprivation and the simulated drowning technique known as waterboarding.

The protective order contains provisions to censor or close proceedings that appear to violate constitutional protections for the right to open trials and will undermine the public's confidence in the military tribunals, said David Schulz, a lawyer for a coalition of media organizations that includes The Associated Press.

"The public right has a constitutional right to know what is being done in its name in this tribunal," Schulz said.

The judge did not rule on the issue; testimony was scheduled to continue on Wednesday.

Mohammed and his four co-defendants face charges that include terrorism, conspiracy and 2,976 counts of murder in violation of the law of war, one count for each known victim of the Sept. 11 attacks at the time the charges were filed.