A excerpt from a Paul press release:
Attorney General Holder stated in a letter to Sen. Paul dated March 4, 2013: "It is possible, I suppose, to imagine an extraordinary circumstance in which it would be necessary and appropriate under the Constitution and applicable laws of the United States for the President to authorize the military to use lethal force within the territory of the United States."
"The U.S. Attorney General's refusal to rule out the possibility of drone strikes on American citizens and on American soil is more than frightening—it is an affront the Constitutional due process rights of all Americans," Sen. Paul said.
Sen. Paul also received a letter in response from Mr. Brennan, clarifying the CIA does not have the power to authorize such operations. Notably missing from Mr. Brennan's response are answers to the myriad other questions Sen. Paul posed to him in previous correspondence.