The civil liberties groups sued in U.S. District Court in Washington after being retained by the father of Anwar al-Aulaqi, a radical U.S.-born cleric who is in hiding in Yemen.

The CIA placed Aulaqi on its list of suspected terrorists it is authorized to kill earlier this year; the cleric had been on a separate list of individuals targeted by the Joint Special Operations Command.

“The United States cannot simply execute people, including its own citizens, anywhere in the world based on its own say-so,” Vince Warren, executive director of the Center for Constitutional Rights, said in a written statement. “That the government adds people to kill lists after a bureaucratic process and leaves them on the lists for months at a time flies in the face of the Constitution and international law.”…

“Whatever people think about the merits of the program, we think at a minimum Americans have a right to know under what circumstances the government has the right to impose the death penalty without charge or trial,” said Jameel Jaffer, director of the ACLU’s National Security Project.