US President Barack Obama says CIA agents who used harsh interrogation techniques on terrorism suspects during the Bush era will not be prosecuted.
Mr Obama banned the use of methods such as sleep deprivation and simulated drowning in his first week in office.
He has now released four memos detailing techniques the CIA was able to use under the Bush administration.
Rights groups have criticised his decision to protect CIA agents involved in the interrogation procedures.
Amnesty International said the Department of Justice appeared to be offering a "get-out-of-jail-free card" to individuals who were involved in acts of torture.
The Centre for Constitutional Rights, which has championed the legal rights of the "war on terror" detainees, also expressed its disappointment.
"It is one of the deepest disappointments of this administration that it appears unwilling to uphold the law where crimes have been committed by former officials," it said in a statement.
Harsh techniques
On Thursday, the Obama administration published four secret memos detailing legal justification for the Bush-era CIA interrogation programme, whose methods critics say amounted to torture.
Announcing the publication of the memos, Mr Obama gave an assurance that "those who carried out their duties relying in good faith upon legal advice from the Department of Justice... will not be subject to prosecution".
One of the documents contained legal authorisation for a list of specific harsh interrogation techniques, including pushing detainees against a wall, facial slaps, cramped confinement, stress positions and sleep deprivation.
The memo also authorises the use of "waterboarding", or simulated drowning, and the placing of a detainee into a confined space with an insect.
Critics of the Bush administration's interrogation programme say the memos provide evidence that many of the methods amount to torture under US and international law.
During his first week in office, President Obama issued an executive order officially outlawing the use of harsh interrogation techniques by the CIA, and forcing the agency to adhere to standards laid out in the US Army Field Manual.
The release of the memos stems from a request by civil rights group the American Civil Liberties Union (ACLU).