Wyden, a member of the Senate Intelligence Committee, has been requesting these documents for years, saying he is concerned that the intelligence community, Justice Department and administration have not been forthcoming with Congress on the legal justifications for targeting U.S. citizens believed to be involved in terrorism against the U.S.

“It is critically important for Congress and the American public to have full knowledge of how the executive branch understands the limits and boundaries of this authority, so that Congress and the public can decide whether this authority has been properly defined, and whether the president’s power to deliberately kill American citizens is subject to appropriate limitations,” the letter stated.

Wyden also asked for a list of countries in which the intelligence community has used its lethal counterterrorism authority, saying that the executive branch's failure to respond has shown that it is “evading congressional oversight.”

Wyden said he would take Brennan’s response to these requests into consideration when deciding whether to support his nomination as director of the CIA. Wyden also warned Brennan that he would face tough questions about the CIA’s use of torture and coercive interrogation during his confirmation process.