A federal judge says the United States can continue to hold some prisoners at Guantanamo Bay indefinitely without any charges.

U.S. District Judge John Bates' opinion issued Tuesday night limited the Obama administration's definition of who can be held. But he said Congress in the days after Sept. 11, 2001 gave the president the authority to hold anyone involved in planning, aiding or carrying out the terrorist attacks.

Bates' opinion comes amid increasing debate over whether President Obama is going to release anyone from Guantanamo. Obama has promised to close the prison by January, but Senate Democrats say they will block the move until he comes up with a plan for the detainees.

Bates' opinion came in the case of several Guantanamo prisoners who are challenging their detention. ACLU attorney Jonathan Hafetz said the opinion "flouts the Constitution's prohibition against indefinite detention without charge."

"The decision wrongly concludes that terrorism suspects at Guantanamo may continue to languish in military detention rather than being prosecuted in our civilian courts," Hafetz said. "Like the president's recent decision to revive military commissions, this ruling perpetuates rather than ends the failed experiment in lawlessness that is Guantanamo."

Earlier this year, Bates ordered the Obama administration to give its definition of whom the United States can continue to hold at Guantanamo. The administration responded with a definition that was largely similar to the Bush administration's, drawing criticism from human rights advocates.

In his opinion, Bates said he agreed with the Obama administration that "the president has the authority to detain persons that the president determines planned, authorized, committed or aided the terrorist attacks that occurred on September 11, 2001, and persons who harbored those responsible for those attacks.

"The president also has the authority to detain persons who are or were part of Taliban or al-Qaida forces or associated forces that are engaged in hostilities against the United States or its coalition partners, including any person who has committed (i.e., directly participated in) a belligerent act in aid of such enemy armed forces," Bates wrote.

But he said the Obama administration went beyond the law of war by including in its definition those who "supported" enemy forces.

"The court can find no authority in domestic law or the law of war, nor can the government point to any, to justify the concept of 'support' as a valid ground for detention," Bates wrote.

Last month, Bates ruled that prisoners at Bagram Airfield in Afghanistan can challenge their detention, for the first time extending rights given to Guantanamo Bay detainees elsewhere in the world.