Three of the Obama administration’s biggest critics on civil liberties and national security have retroactively endorsed the killing of American Anwar al-Awlaki, the alleged al Qaeda preacher who was died in a 2011 drone strike in Yemen.

In a letter signed by Democratic senators Ron Wyden of Oregon, Mark Udall of Colorado, and Martin Heinrich of New Mexico, the lawmakers argue that “the decision to use lethal force against Anwar al-Awlaki was a legitimate use of authority granted to the president.”

Prior to leaks facilitated by former NSA contractor Edward Snowden, the Obama administration was facing harsh criticism from civil liberties advocates over the claim that it has the authority to use lethal force against U.S. citizens it suspects of engaging terrorism abroad.

Last March, Wyden threatened to hold up Obama’s nominee to head the Central Intelligence Agency unless the administration disclosed its legal rationale for the use of lethal force against American terror suspects abroad. The administration ultimately agreed to share more information, shortly before Kentucky Republican Senator Rand Paul mounted a near 13-hour filibuster against John Brennan’s nomination.

The letter states that while the U.S. government did not “publicly acknowledge” that it was targeting al-Awlaki, leaks to the media had “served as the modern equivalent of a wanted poster,” and that al-Awlaki could have turned himself in and cleared his own name had he been innocent. Furthermore, they write, “lethal force appears to have been used against Mr. Al-Awlaki in a manner consistent with applicable international law.”

Prior to al-Awlaki’s death, his guilt or innocence were litigated largely in the public sphere, rather than a court of law. After his death, the Obama administration released documents they said were recovered from Osama bin Laden’s compound that pointed to al-Awlaki being a high-ranking member of Al Qaeda in the Arabian Peninsula.

While the letter endorses the decision to take lethal action against al-Awlaki and the legal rationale under which that action was taken, it is not entirely uncritical of the administration. The senators argue that “the limits and boundaries of the president’s power to authorize the deliberate killing of Americans need to be laid out with much greater specificity,” to both “Congress and the public.” The letter also states that the administration should provide more information about how it determines who is targetable and who is a civilian, and how it evaluates civilian casualties after the fact.

The letter does not mention Abdulrahman al-Awlaki, al-Awlaki’s teenage son, who was killed in a subsequent drone strike in Yemen shortly afterwards. His death was reportedly a mistake.