US judge: Guantanamo evidence must be made public

* Decision involved more than 100 cases by prisoners

* Victory for detainee lawyers, news organizations

(Adds Justice Dept. comment)

By James Vicini

WASHINGTON, June 1 (Reuters) - A federal judge rejected on Monday a U.S. government request to keep secret the unclassified evidence that it says justifies the continued imprisonment of more than 100 Guantanamo Bay prisoners.

U.S. District Judge Thomas Hogan ruled the government cannot keep the documents known as factual returns from public disclosure and must seek court approval to keep specific information secret.

"Public interest in Guantanamo Bay generally and these proceedings specifically has been unwavering," Hogan wrote. "Publicly disclosing the factual returns would enlighten the citizenry and improve perceptions of the proceedings' fairness."

U.S. President Barack Obama had vowed to close the detention center set up at the U.S. Naval Base in Cuba by his predecessor George W. Bush to hold foreign terrorism suspects after the Sept. 11, 2001 attacks. But closing the center has proved difficult as the White House grapples with where to place the remaining prisoners.

The sealed court documents outlined the government's case for the continued holding of the detainees. The documents were filed in response to petitions by the detainees seeking their court-ordered release.

The ruling was a victory for detainee lawyers and a coalition of news organizations. They argued the news media and the public have a constitutional right of access to the documents.

The judge ordered the U.S. Justice Department to publicly file its unclassified records or show the court what specific information it wants to keep secret by the end of next month.

Jonathan Hafetz, an attorney with the American Civil Liberties Union, hailed the ruling.

"For far too long, the government has succeeded in keeping information about Guantanamo secret and used secrecy to cover-up illegal detention and abuse," he said. "The decision marks an important step towards restoring America's open court tradition that is essential to both accountability and the rule of law."

The Justice Department was reviewing the ruling, spokesman Dean Boyd said. He said the government never sought to keep the information sealed indefinitely but only until the completion of an appropriate classification review. (Editing by Jackie Frank)