Members of the American Psychological Association have voted to prohibit psychologists from working at locations, like the Guantánamo Bay detention center, where suspected terrorists are being held outside the framework of the Geneva Conventions or the U.S. Constitution, the association announced on Wednesday.

The resolution was approved in a mail ballot by a vote of 8,792 to 6,157. The ban contains an exception for psychologists who “are working directly for the persons being detained or for an independent third party working to protect human rights.” It will take effect in August 2009, when the association holds its next annual meeting.

The new policy will not be legally binding, but many states’ licensing boards ask psychologists if they have ever been the subject of ethics investigations within their professional associations.

The referendum marks the latest phase in a long battle over psychologists’ roles in the interrogation of prisoners and detainees. In a statement released yesterday, the referendum’s authors called on the association “to investigate and create a public record regarding the participation of U.S. psychologists in torture and other detainee abuse.”

The resolution’s opponents argued that its language was so broad and ambiguous that it might prohibit benign work by psychologists in prisons and psychiatric hospitals.

Next week the Senate Armed Services Committee will hold a hearing on allegations that psychologists contributed to abusive interrogations in Iraq by “reverse-engineering” a training program designed to help U.S. soldiers survive capture and torture by enemy forces. —David Glenn