The Senate confirmed John Brennan as director of the CIA on Thursday, following a 13-hour filibuster led by Sen. Rand Paul (R-Ky.).

Brennan, the current White House counterterrorism chief, was approved to head the CIA, 63 to 34. The confirmation came after weeks of contentious hearings concerning Brennan’s ties to the administration’s armed drone program, and was capped by Paul’s old-fashioned filibuster..

Brennan could begin his tenure as CIA director as early as this week.

Paul began filibustering the nomination on Wednesday, demanding that the Obama administration state clearly that the armed drone program would not be used against American citizens on American soil. On Thursday, Attorney General Eric Holder sent a letter to Paul, stating that the administration has no right to target and kill American citizens on U.S. soil.

“Does the president have the authority to use a weaponized drone to kill an American not engaged in combat on American soil? The answer is no. The answer to that question is no,” according to Holder’s letter, read to reporters by White House press secretary Jay Carney.