The Convention against Torture and other cruel, inhuman or degrading treatment or punishmentAdopted by the UN General Assembly on December 10, 1984
Signed by the US on April 18, 1988
Ratified by the US on Oct. 21, 1994
Entered into force on June 26, 1987.
Article 2
1. Each State Party shall take effective legislative, administrative, judicial or other measures to prevent acts of torture in any territory under its jurisdiction.
2. No exceptional circumstances whatsoever, whether a state of war or a threat of war, internal poltiical instability or any other public emergency, may be invoked as a justification of torture.
3. An order from a superior office or a public authority may not be invoked as a justificatin of torture.
Article 3
1. No state Party shall expel, return (refouler) or extradiate a person to another State where there are substantial grounds for believing that he would be in danger of bein subjected to tortuore.
2. For the purpose of determining whether there are such grounds, the competent authorities shall take into account all relevant considerations including, where kapplicabhle, the existence in the STate concerned of a consistent pattern of gross, flagrant or mass violations of human rights.
This is the only reservation I found for the US:
United States of America
"The United States declares, pursuant to article 21, paragraph 1, of the Convention, that it recognizes the competence of the Committee against Torture to receive and consider communications to the effect that a State Party claims that another State Party is not fulfilling its obligations under the Convention. It is the understanding of the United States that, pursuant to the above-mentioned article, such communications shall be accepted and processed only if they come from a State Party which has made a similar declaration."
There is also this:
11. On 3 June 1994, the Secretary-General received a communication from the Government of the United States of America requesting, in compliance with a condition set forth by the Senate of the United States of America, in giving advice and consent to the ratification of the Convention, and in contemplation of the deposit of an instrument of ratification of the Convention by the Government of the United States of America, that a notification should be made to all present and prospective ratifying Parties to the Convention to the effect that:
"... nothing in this Convention requires or authorizes legislation, or other action, by the United States of America prohibited by the Constitution of the United States as interpreted by the United States."