The Obama administration said on Wednesday that it will not seek new legislation from Congress authorizing the indefinite detention of about 50 terrorism suspects being held without charges at Guantanamo Bay. While that still upsets many civil libertarians who say the United States never ought to detain anyone indefinitely without charge, it’s at least better than the alternative, which some worried would have been broad new legislation that could have expanded U.S. detention authority beyond what it claims it has now.

Since Sept. 11 terrorist attacks,  the United States has claimed it has the authority to indefinitely detain fighters in the “war on terror” according to the laws of war. Critics counter that the fight against terrorism isn’t a “war” that allows the United States to take prisoners, and of course when it came time to granting detainees prisoners-of-war status, the Bush administration adamantly refused.

When President Obama said in his speech at the National Archives in June that he still believes there’s a category of people at Guantanamo who can’t be tried in criminal court or by military commission but are too dangerous to release, he sparked a vigorous debate about just what kind of “preventive detention” scheme the president can or should embrace.

The American Civil Liberties Union, among others, insisted that any sort of “indefinite detention,” whether by legislation or executive order, would simply be extending the unconstitutional Bush policy that Obama criticized before he took office. But some lawyers, worried that taking a hard line would lead to the adoption of a broad new detention policy that would extend beyond the detainees at Guantanamo, urged the administration to stick to the detention authorization that it already has under the laws of war.

That camp apparently won the battle.  On Wednesday, the administration said it will continue to hold the Guantanamo detainees without charge or trial based on the power it claims pursuant to the Congressional resolution passed after the attacks of Sept. 11, 2001, authorizing the president to use force against al-Qaeda and the Taliban.

On Thursday, the ACLU registered its disappointment.

“While the Obama administration is wise not to seek legislation or issue an executive order that would formalize an unconstitutional system of indefinite detention, it remains deeply troubling that the administration continues to maintain a de facto system in which detainees are held indefinitely without charge or trial,” said Anthony Romero, Executive Director of the ACLU, in a statement.

“Locking people up indefinitely without charge or trial violates our most fundamental laws and values. … It is important to keep in mind that even with today’s development, what we are left with is a continuation of the misguided detention policy of the Bush administration.”

Holder also wouldn’t speculate as to how many people — if any — may fall into that category, though he reiterated that President Obama has maintained that he has that right to detain such “dangerous” people.

“We’re going to have ideas” about how to decide who to detain indefinitely and what sort of legal process they’re due, “but we want to interact with members of the committee so it has the support of Congress,” Holder said.

Obama’s plan for “preventive” indefinite detention for some detainees “who cannot be prosecuted yet who pose a clear danger to the American people,” as he described in in a May 21 speech at the National Archives, remains a point of contention in Congress and among many legal experts and civil liberties advocates.

This morning’s hearings made clear that the controversy over the use of “preventive detention” to indefinitely imprison detainees in the “war on terror” that the administration believes cannot be charged is far from over.