The campaign group, Human Rights Watch, has accused the United States Government of secret arrests, arbitrary detentions and of violating due process in its response to the 11 September attacks.
In a new report, Human Rights Watch says more than 1,200 non-American citizens have been secretly arrested and jailed - the vast majority from the Middle East, North Africa and South Asia.
Many, it says, have been subjected to treatment in violation of American law.
Human Rights Watch says the US Government has held some detainees for prolonged periods without charge, and has blocked their access to lawyers, while subjecting them to hostile, coercive interrogations.
Democratic values
In some cases, detainees have been held in solitary confinement, and have been physically and verbally abused because of their national origin or religion.
The Justice Department has refused to reveal exactly how many non-Americans have been detained since 11 September. But Human Rights Watch says it believes it is more than 1200.
Its report details cases in which detainees were picked up arbitrarily, following random encounters with the police or immigration officials or after neighbours reported suspicions based on the detainees religion or nationality.
The American government, Human Rights Watch argues, is behaving in a manner incompatible with democratic values, holding court hearings in secret and refusing to release the names and whereabouts of those detained.
It calls on the authorities here to take steps at once to right the situation.