US President Barack Obama has the legal authority to use an unmanned drone strike to kill his own citizens on American soil.
This is the extraordinary admission in a leaked memo from the US attorney-general Eric Holder.
Mr Holder suggested that using a drone to kill an American on home territory would be justified and permissable in "extraordinary circumstances", comparable to the terrorist attacks of 11 September 2001.
But he added that it was "entirely hypothetical" and "unlikely to occur".
Quizzed about the memo in front of a Senate judiciary committee on Wednesday, Mr Holder emphasised that "the government has no intention to carry out any drone strikes in the United States".
But Senator Chuck Grassley, a Republican from Iowa, told him the use of the phrase "extraordinary circumstances" was "extremely concerning".