On Thursday, Holder wrote to Paul a two-sentence letter:

"It has come to my attention that you have now asked an additional question: 'Does the President have the authority to use a weaponized drone to kill an American not engaged in combat on American soil?' The answer to that question is no."

Feinstein said on the Senate floor moments after that letter was released that Paul now has his answer and that the GOP should allow for votes.

"So hopefully the question of continuing this will be vitiated, and we will be able to proceed with a vote," she said.

"This is not permitted in the United States of America," she said of the notion of using drones to kill Americans in the country. "The Attorney General, by his letter, has said just that. It will not happen. I hope this puts this to an end."

After Paul was done speaking early Thursday morning, Democrats filed a motion to end debate on the Brennan nomination. Without an agreement among senators to speed it up, that vote could happen Saturday at the earliest.

Paul had yet to speak on the floor about the Holder letter since the Senate resumed work at 2 p.m.