[1] Before becoming a federal judge, Katsas served as Deputy White House Counsel to President Donald Trump, as an assistant attorney general in the United States Department of Justice, and as a partner at the law firm Jones Day.

[6][5] Katsas then entered private practice at the Washington, D.C., office of the law firm Jones Day, where he specialized in civil and appellate litigation.

On September 7, 2017, President Donald Trump nominated Katsas to serve as a United States circuit judge of the United States Court of Appeals for the District of Columbia Circuit, to the seat vacated by Judge Janice Rogers Brown, who retired on August 31, 2017.

[17][18] In 2017, Katsas recused himself from matters regarding the Mueller probe on which he personally worked, but said he would consider the facts of a case before making a decision.

[22] On April 7, 2023, Katsas authored a dissent in Fischer v. United States, a case interpreting whether January 6 participants could be charged under 18 U.S.C.

§ 1512(c), a provision of the Sarbanes–Oxley Act enacted to combat corporate fraud that penalizes anyone who “otherwise obstructs, influences, or impedes any official proceeding.”[23] Rejecting the government’s argument, Katsas argued that interpreting “the structure and history of section 1512, and with decades of precedent applying section 1512(c) only to acts that affect the integrity or availability of evidence” suggest that the government’s reading is “implausibly broad and unconstitutional in a significant number of its applications.”[24] He is a member of the Federalist Society,[25] and also a member of the American Academy of Appellate Lawyers.