WASHINGTON (CNN) -- A federal appeals court Friday let stand its ruling giving judges greater power to review government evidence against accused terrorists challenging their imprisonment.
More than 300 foreign nationals are being held at the U.S. Navy Base at Guantanamo Bay, Cuba.
The decision hands the Bush administration another legal setback over its policies on foreign detainees.
The U.S. Court of Appeals for the District of Columbia split 5-5 over whether to grant a full hearing.
That upheld a ruling by a three-judge panel last July that the U.S. military could not limit what information the courts hear when foreign detainees seek freedom.
The government had argued national security concerns gave them the discretion to decide what documents were pertinent for judicial review.
The Justice Department now has the option of appealing to the Supreme Court, but any further review may not happen until autumn at the earliest.
About 380 foreign nationals are being held at the U.S. Navy Base at Guantanamo Bay, Cuba. The detainees' lawyers have complained the government is also unfairly restricting access to potential evidence that could clear their clients, evidence they may not even know exists.
Those hearings -- known as combatant status review tribunals (CSRT) -- determine whether a prisoner can be designated an "enemy combatant" and prosecuted by the military.
A federal law passed in 2006 -- the Detainee Treatment Act -- restricts the ability of accused "enemy combatants" to challenge trial procedures and findings before the D.C. Circuit federal appeals court.
"The DTA requires that the record on review of a CSRT's status determination include all government information," wrote Chief Judge Douglas Ginsburg.
The judge noted the system set up by the military is not similar to civilian trials, because defense lawyers are not allowed to attend, and the prosecution does not have to turn over evidence that may help prove the prisoner's innocence.
"For this court to ignore that reality would be to proceed as though the Congress envisioned judicial review as a mere charade when it enacted the DTA."
The Supreme Court is considering a separate appeal over the constitutionality of the military tribunal system itself.
At issue are the rights of the detainees to contest their imprisonment and the rules set up to try them. A wide range of proposed procedures is being challenged, and the high court is expected to issue its rulings by late June.
Some judges on the appeal panel worried further review by them would delay the high court's decision.
The legal issues surrounding the foreign nationals held in U.S. custody have reached greater urgency in recent months. Many of the men are going on their sixth year of detention, and several have already had pretrial hearings before the military tribunal.
These latest appeals involve Chinese national Hozaifa Parhat and Afghan Haji Bismullah.
Parhat, a Muslim of ethnic Uighur descent, is accused of attending a terror training camp in Afghanistan at the time of the September 11, 2001, attacks.
Bismullah, 28, is accused of fighting with the Taliban against the United States and its Afghan allies.
In a dissent, Judge Raymond Randolph issued an unusually sharp rebuke of the ruling, saying the government believes it "endangers national security."
"We think it is more important to decide the case correctly," wrote Randolph, "and that a correct decision would be of more assistance to the high court."
The justices have twice limited the government's power to detain and prosecute foreign nationals held at Guantanamo.
In a small victory for the government, the full appeals court did agree that only the judges themselves could view top secret declarations from intelligence officials. Neither the defense lawyers nor the judges' staff will be allowed access.
The government has complained unlimited lawyer access and the current mail system threaten national security, because some detainees were informed about ongoing terror activities and U.S. efforts to fight them.
The proposed rules would allow officials to censor mail to intercept certain details the government determined would compromise national security. E-mail to a friend