In a scathing statement, the head of the ACLU, and other leading civil liberties and human rights groups who were among President Obama's most ardent campaign supporters said the President's decision to sign a sprawling defense bill including controversial detainee provisions would tarnish his legacy.

While voicing reservations, Obama reportedly signed the act because it guarantees continued military funding. He promised the provisions would comply "with the Constitution, the laws of war, and all other applicable law."

But human rights groups on the left say future presidents may apply the law differently, adding the act is a sweeping expansion of executive power -- beyond what was seen under the Bush administration. The ACLU and others slammed the president for putting his name to this year’s National Defense Authorization Act, or NDAA, out of concern that it would continue to allow indefinite detention while mandating military custody for some detainees.

The ACLU and others slammed the president for putting his name to this year’s National Defense Authorization Act, or NDAA, out of concern that it would continue to allow indefinite detention while mandating military custody for some detainees.

"President Obama's action ... is a blight on his legacy because he will forever be known as the president who signed indefinite detention without charge or trial into law," ACLU Executive Director Anthony Romero said.

The national Muslim rights group CAIR slammed the legislation "as a stain on our nation's history -- one that will ultimately be viewed with embarrassment and shame."

And the senior counterterrorism counsel and advocate for Human Rights Watch, Andrea Prasow, chastised the president even before the act was signed.

“I think the president really has to veto this bill because codifying indefinite detention in the U.S., mandating military detention for all terrorism suspects found inside the U.S., really sets the U.S. back decades in terms of how we approach terrorism,” Prasow said.

The Center for Constitutional Rights, or CCR, said the NDAA kills any prospect for relocating detainees and shuttering the Guantanamo camps because it requires the defense secretary to certify that the transferred men will not commit hostile acts in the future.

In a statement, CCR said "the same presidential signature that ordered the closing of Guantánamo almost three years ago, has now ensured their release or transfer is practically impossible. "

On the detention of American citizens, critics say section 1021 of the act is overly broad because it does not rule out indefinite detention and "...includes the authority for the Armed Forces of the United States to detain covered persons."

Section 1022, which makes military custody mandatory for a subset of detainees, does make an exception for U.S. citizens and legal permanent residents.

On New Year's eve, in a 1,800-word signing statement, the president seemed to emphasize the point, claiming: "my administration will not authorize the indefinite military detention without trial of American citizens."

Fox News Chief Intelligence Correspondent Catherine Herridge's bestselling book "The Next Wave: On the Hunt for al Qaeda's American Recruits" was published by Crown on June 21st. It draws on her reporting for Fox News into al-Awlaki and his new generation of recruits -- al Qaeda 2.0. It is the first book to full investigate al-Awlaki’s American life, his connections to the hijackers, and how the cleric double crossed the FBI after Sept. 11.