The United Nations formally launched an investigation into the United States’ targeted killing program on Thursday morning. Ben Emmerson, the U.N.’s special rapporteur on counterterrorism and human rights, announced the beginning of the inquiry at a press conference in London.

“The central objective of the present investigation is to look at the evidence that drone strikes and other forms of remote targeted killing have caused disproportionate civilian casualties in some instances,” he said, “and to make recommendations concerning the duty of States to conduct thorough independent and impartial investigations into such allegations, with a view to securing accountability and reparation where things can be shown to have gone badly wrong with potentially grave consequences for civilians.”

While Emmerson said his investigation while concern “all use of armed force…for the purpose of targeted killing,” he stressed that “it is the use of drones which has propelled this issue to the top of the international agenda” because of the ease with which the relatively new technology can be deployed.

The American Civil Liberties Union, which has filed several lawsuits challenging the legality of the Obama administration’s targeted killing program, said it welcomed the investigation.

“Virtually no other country agrees with the U.S.’s claimed authority to secretly declare people enemies of the state and kill them and civilian bystanders far from any recognized battlefield,” said ACLU National Security Project director Hina Shamsi in a statement. “To date, there has been an abysmal lack of transparency and no accountability for the U.S. government’s ever-expanding targeted killing program.”

The ACLU Human Rights Program’s director, Jamil Dakwar, said, “We hope the U.S. cooperates with the inquiry, and whether it does or not will show whether it holds itself to the same obligation to cooperate with U.N. human rights investigations that it urges on other countries.”

As President Obama enters his second term, there are signals that he intends to continue the targeted killing program indefinitely. The administration has been working on codifying official rules for the program since shortly before the end of the 2012 election, though there have been recent reports that these rules would exempt the CIA’s Pakistan drone campaign entirely.

Obama may have also signaled his intent to go all-in on drone warfare when he nominated counterterrorism adviser John Brennan to become director of the CIA. Brennan, known by his critics as the White House’s “assassination czar,” has long been one of the key officials involved in developing and implementing the administration’s targeted killing program.

In President Obama’s second inaugural address, he said, “We, the people, still believe that enduring security and lasting peace do not require perpetual war. ” Similarly, in a recent interview, Defense Secretary Leon Panetta said drones were “not something that we’re going to have to continue to use forever.” However, in the same interview, he also described drone attacks as ”a continuing tool of national defense in the future.”