WASHINGTON — Civil libertarians want to challenge as unconstitutional the Obama administration’s use of “targeted killings” against accused terrorists overseas, including Anwar al-Awlaqi, an American citizen in Yemen who is said to be working with al-Qaida.

But they say they have been stymied by an unusual Bush-era regulation that requires lawyers to get permission from the Treasury Department before they sue the government on behalf of a “designated global terrorist.”

On Tuesday, the American Civil Liberties Union and the Center for Constitutional Rights filed suit in a federal court here, asking a judge to clear the way for a broader challenge to the military’s use of “targeted killings” far removed from a battlefield.

“The government is targeting an American citizen for death without any legal process whatsoever, while at the same time impeding lawyers from challenging that death sentence and the government’s sweeping claim of authority to issue it,” said Anthony Romero, executive director of the ACLU. “We don’t think lawyers should have to obtain permission to bring a lawsuit against the government.”

Hours after the suit was filed, a Treasury Department official said his agency would not stand in the way of a lawsuit filed on behalf of a designated “global terrorist.”

The Obama administration has increasingly used aerial drones to attack and kill al-Qaida leaders. In April, the administration put al-Awlaqi on its target list. He is an American-born Muslim cleric who lives in Yemen and has reportedly encouraged a series of attacks on the United States, including the failed Christmas Day bombing of an airplane arriving in Detroit.