Millett's 2013 nomination to the D.C. Circuit, along with the nominations of Robert L. Wilkins and Nina Pillard, ultimately became central to the debate over the use of the filibuster in the United States Senate, leading to the use of the so-called "nuclear option" to bring it to the Senate floor for a vote.
In 2007, Millett joined the Washington, D.C. law firm of Akin Gump Strauss Hauer & Feld, co-chairing the firm's Supreme Court practice along with Tom Goldstein.[1] At Akin Gump, her victories included Samantar v. Yousuf, in which she represented victims of torture who argued that the Foreign Sovereign Immunities Act did not grant immunity to former foreign government officials.
On February 26, 2009, the Virginia State Bar separately deemed Millett to be "highly qualified" for the vacancy, along with Edwards, Keenan, and attorney Richard A. Simpson.[9] Keenan was nominated by President Obama to fill the vacancy on September 14, 2009, confirmed by the Senate on February 26, 2010, and sworn in on March 9, 2010.
On October 28, 2013, Senate Majority Leader Harry Reid motioned to invoke cloture on Millett's nomination.[14] On October 31, 2013, the motion to invoke cloture was rejected by a 55–38 vote, with 3 senators voting "present."[15]
On November 21, 2013, the motion to invoke cloture was rejected again, by a 57–40 vote with 3 senators voting "present".[16] A motion to reconsider the motion to invoke cloture was held shortly thereafter and was agreed to by a 57–43 vote.[17] Senator Reid then requested a ruling from the presiding officer regarding the filibuster of judicial nominees. The President pro tempore ruled that the Senate required 60 votes to cut off a filibuster and move to a final vote. Senator Reid appealed that ruling and the Senate began voting on whether the President pro tempore's ruling should stand, setting up a vote on what is colloquially known as the "nuclear option." The ruling was not sustained by a 48–52 vote.[18] As a result of that vote, the President pro tempore ruled that as of November 21, 2013, the threshold for invoking cloture on all executive branch nominees, and all district and circuit court nominees would be a simple majority of senators present and voting. Senator Mitch McConnell, the Senate Minority Leader, immediately requested an appeal of that ruling; that appeal failed by a 52–48 vote.[19] The Senate then began voting on the motion to invoke cloture under the new majority-vote threshold. Cloture was subsequently invoked on her nomination by a 55–43 vote with 2 senators voting "present".[20][21] On December 10, 2013, the Senate confirmed Millett by a 56–38 vote.[22] She received her commission the same day.[5]
After the death of Supreme Court justice Antonin Scalia on February 13, 2016, Millett's name was among those mentioned by court-watchers as a possible successor.[23][24] President Obama ultimately nominated her D.C. Circuit colleague, Judge Merrick Garland.[25]
In November 2021, Millett dissented in a case that struck down the EPA's fuel efficiency standards for trailers on trucks.[28][29]
In December 2021, Millett wrote the majority opinion in a case brought by former president Donald Trump to block the release of presidential records that the congressional committee investigating the January 6, 2021, attack on the U.S. Capitol.[30]