Releasing the names of those detained after Sept. 11 would threaten national security by identifying witnesses and other details of the government's terrorism investigation, Justice Department lawyers argued Monday.

"This is not secrecy for secrecy's sake," Assistant U.S. Attorney General Robert McCallum told a three-judge state appeals panel.

The judges heard arguments over a lawsuit filed in January by the American Civil Liberties Union of New Jersey. The group wants to have names released for hundreds of federal detainees held in New Jersey jails.

The appellate panel issued no decision Monday.

The ACLU argues that state law requires the Hudson and Passaic County jails to release the names of all inmates, even those detained by the U.S Immigration and Naturalization Service. The ACLU has said it wants the names so it can offer legal representation and assess how well they are being treated while in custody.

Superior Court Judge Arthur D'Italia ruled in the ACLU's favor in March. The Justice Department appealed, and INS officials issued an April 17 memo ordering state and county officials not to release any names.

McCallum said disclosing the names of some detainees could deter them from cooperating in the investigation and could let terrorists know what information the government has gathered, leading to "potentially extraordinarily dangerous" consequences.

Unlike a separate federal lawsuit seeking the release of detainees' names around the country, the New Jersey lawsuit uses state laws to back up its argument.

Appellate judge Howard Kestin asked another Justice Department lawyer, Thomas Bondy, why the government had not anticipated the conflict between state and federal laws earlier.

"It never occurred to us that a court would actually do this," Bondy replied, referring to D'Italia's order.

Bondy argued that federal law and the INS' April 17 directive should be followed in all detainee cases.

"It doesn't matter what state law provides here," he said.

That drew concern from the judges.

"For a government to say we lost in this case and we're going to cure it by promulgating a regulation, it's troubling," Kestin said.

Arlene Turinchak, representing the North Jersey Media Group, argued that keeping the names secret is threatening the public's right of government oversight, which she called "a principal foundation of our democracy."

The media group owns The Record of Hackensack and the Herald News of West Paterson.