The letter, from Stephen D. Kelly, the FBI's assistant director of congressional affairs, said the agency doesn't use drones for general surveillance unrelated to specific investigations. An earlier FBI letter said none of its drones have been armed.
Monday's letter said the FBI's use of drones must comply with constitutional privacy protections and agency guidelines and meet "the definition of a reasonable expectation of privacy provided by the Supreme Court."
However, the letter said that while the top court has not ruled on the use of drones, prior rulings on aerial surveillance held that court warrants were not needed because the areas monitored were open to public view and "there was no reasonable expectation of privacy."
The agency also wrote that a warrant would not be needed because drones don't physically trespass on private property.
"I disagree with this interpretation," Paul said in a written statement. He said he agreed to allow the Comey vote "given the fact that they did respond to my concerns over drone use on U.S. soil."
Democratic leaders were hoping the Senate would confirm three Democratic nominees to the five-member National Labor Relations Board on Tuesday: Mark Gaston Pearce, the board's current chairman, and Kent Hirozawa and Nancy Schiffer, who have both been long-time labor lawyers.
Votes on ending procedural delays against the nominations of Power and Jones were expected Wednesday. Supporters will need 60 of the Senate's 100 votes to remove those procedural roadblocks.
Votes also seem likely this week on two Republican nominations to the NLRB: Chicago attorney Philip A. Miscimarra and Los Angeles lawyer Harry I. Johnson III, who have both worked with employers on labor issues.