WASHINGTON -- A federal judge ruled Wednesday that lawyers for an Afghan man held at Guantánamo Bay cannot see top secret information that she acknowledges would be helpful to his case.

U.S. District Judge Rosemary Collyer said in an opinion that the information could bolster efforts to win the release of suspected Taliban and al-Qaida financier Wali Mohammad Morafa, 46. But Collyer said the information identifying a confidential source is too sensitive to provide to the man’s lawyers, who have clearance to see secret, but not top-secret, material.

Collyer, an appointee of Republican President George W. Bush, says her ruling is a “minor detriment” to Morafa, but that it is more important that she has been able to review the information.

“This court concludes and finds that top-secret information of the kind at issue here must be available to the neutral decision-maker even if not disclosed to Mr. Morafa’s counsel,” she said.

Morafa, previously identified as Wali Mohammad, got to Guantánamo in May 2002. He has never been charged with a crime there.

He has denied doing business with the Taliban or al-Qaida. Instead, he said he was a businessman who was handed over to the Americans by Pakistani intelligence agents because he would not pay a bribe.

Suspected terrorists held at Guantánamo have a constitutional right to contest their detention, under the Supreme Court’s 2008 decision in Boumediene v. Bush. But that case gave much discretion to lower court judges, including over how to handle sensitive information.

In many instances, the government is able to satisfy detainee lawyers’ demands for information by providing edited versions of highly classified documents.

But in this case, Collyer said, the relevant information cannot be scrubbed sufficiently to hand it over. Still, she said, the lawyers have been given access to the substance of the information provided by the source, just not the identity.

Also, she said, most important in the legal process the high court ratified in 2008 is that a judge has enough information to determine whether someone is being properly held. Collyer said she has been able to review all relevant materials.