The US Supreme Court has allowed the Bush administration to keep secret the names and other basic details of terror suspects it has detained.
A wave of arrests followed the 11 September attacks
Hundreds of people were arrested or detained and questioned in the US after the 11 September 2001 attacks.
The US court refused to hear an appeal by civil liberties groups challenging the arrests as violating the Freedom of Information Act and free speech rights.
Judges ruled that disclosing the names could harm US national security.
Nearly all of the people detained or arrested by US authorities in the US following the 9/11 attacks were Arabs or Muslims - many from Pakistan.
Some were charged with crimes while others were held as material witnesses.
Only Zacarias Moussaoui, a French citizen who was detained before the 11 September attacks, has been named as being prosecuted in connection with the attack that destroyed the World Trade Center.
Between 800 and 1,100 people were detained after 9/11, but about 515 of them were later deported, according to Kate Martin, director of the Washington-based Center for National Security Studies (CNSS).
The CNSS sued to learn the names and other basic information about the detainees.
But the US federal appeals court said last June such information would play into the hands of terrorist groups and ruled the details should be kept secret.
The subsequent legal challenge by the CNSS posed constitutional questions under the First Amendment right to freedom of speech and freedom of the press, and legal questions under the federal Freedom of Information Act.
"It is the responsibility of courts, and especially this court, to provide meaningful judicial review when the government invokes national security to justify unprecedented secrecy in exercising its awesome power to arrest and detain hundreds of people," lawyers argued in their most recent court filing.
"History shows that, in times of crisis and fear, executive officials are prone to overreact, especially in their treatment of minorities in their midst," the appeal said.
Kate Martin - a lawyer in the case - told BBC News Online she was very disappointed by Monday's ruling.
"We're afraid the Justice Department will be free to repeat these abuses in the future and hold more suspects without charges in secret."
She said the only remaining avenue to have the hundreds of detained "terror suspects" named now was through Congress.
"Congress could remedy this ruling by demanding the justice department should release the names, but so far it hasn't," she said.
"We are going to continue lobbying them for this to happen."
The lawyers argued the US Government had sealed immigration records and omitted detainees' names from jail rosters, among other tactics, to make sure that details of hundreds of arrests remained secret.
The US Supreme Court ruled the information would remain secret, without adding any further comment.
The high court has agreed to hear other cases arising from the administration's war on terror.
Other cases involve the president's power to detain American citizens captured abroad and declared "unlawful combatants," and whether foreigners can use American courts to challenge their incarceration at the US military base at Guantanamo Bay in Cuba.