Clive A. Stafford Smith, a lawyer who represents 35 detainees, said one of his clients, Omar Deghayes, a Libyan, had said that in lawyer-client meetings at Guantánamo, “we all know that everything we say in these rooms is being monitored by them.” Military officials say they do not eavesdrop on those meetings.

Mr. Stafford Smith also said several of his clients had described what he said were efforts by Guantánamo officials to foster detainees’ distrust of the lawyers. He said detainees had described investigators’ telling them that their lawyers were Jewish or gay or that prisoners with lawyers were less likely to be released than those without them.

Mr. Stafford Smith and other lawyers also said clients had told them of investigators who posed as lawyers and then questioned detainees.

The military denies Smith's claims. Yet, it can't deny they have seized legal mail from the detainees.

Court records show that the detainees’ concerns about whether lawyers’ mail will remain confidential may be based, in part, on experience. Officials acknowledged in court last year that during an investigation after three suicides at Guantánamo in June they seized written materials and personal items from all detainees, a total of more than 1,100 pounds, “including legal material and other correspondence.”

Other lawyers point to the restrictions imposed on what they can do for their clients, the setbacks in the courts for those challenging their detentions and the length of time they've been incarcerated.

“Every lawyer is afraid, every time they go down there, that their clients won’t see them,” said Mark P. Denbeaux, a professor at Seton Hall University School of Law who represents two Guantánamo detainees. “And it’s getting worse, because it’s pretty hard to say we’re offering them anything.”