Defense lawyers preparing for the war crimes trial of a 21-year-old Guantánamo detainee have been ordered by a military judge not to tell their client  or anyone else  the identity of witnesses against him, newly released documents show.

The case of the detainee, Omar Ahmed Khadr, is being closely watched because it may be the first Guantánamo prosecution to go to trial, perhaps as soon as May.

Defense lawyers say military prosecutors have sought similar orders to keep the names of witnesses secret in other military commission cases, which have been a centerpiece of the Bush administration’s policies for detainees at Guantánamo Bay, Cuba.

Some legal experts and defense lawyers said the judge’s order, issued on Oct. 15 without public disclosure, underscored the gap between military commission procedures and traditional American rules that the accused has a right to a public trial and to confront the witnesses against him.