A federal judge has dismissed a lawsuit filed against the US government by the families of three American citizens killed by US drones in Yemen.
Anwar al-Awlaqi, a New Mexico-born militant cleric who joined al-Qaeda's Yemen affiliate, his teenage son Abdulrahman, and Samir Khan, a naturalised US citizen who moved to Yemen in 2009 to work on Inspire, an al-Qaeda magazine, were all killed in 2011.
Their families sued, claiming the killings were illegal.
Judge Rosemary Collyer of the US District Court in Washington threw out the case, which had named as defendants former defence secretary and CIA chief Leon Panetta, former senior military commander and CIA chief David Petraeus and two others.
"The question presented is whether federal officials can be held personally liable for their roles in drone strikes abroad that [target] US citizens," Collyer said. "The question raises fundamental issues regarding constitutional principles, and is not easy to answer."
However, Collyer said officials "must be trusted and expected to act in accordance with the US Constitution when they target a US citizen abroad at the direction of the president and with the concurrence of Congress. They cannot be held personally responsible in monetary damages for conducting war".
The American Civil Liberties Union, representing the families, said the killings violated constitutional rights to due process.
"This is a deeply troubling decision that treats the government's allegations as proof while refusing to allow those allegations to be tested in court," ACLU lawyer Hina Shamsi said. "The court's view that it cannot provide a remedy for extrajudicial killings when the government claims to be at war, even far from any battlefield, is profoundly at odds with the Constitution."