If former Deputy White House Counsel Gregory Katsas had first-day jitters at his debut oral argument Monday, the newest judge at the U.S. Court of Appeals for the D.C. Circuit didn't show it.

Katsas, nominated by President Donald Trump last September and appointed to the court in December, did not hold back when it came to questioning attorneys on both sides of the two cases he heard Monday morning. Katsas remained engaged throughout the roughly two-and-a- half-hour-long hearing, asking pointed questions about factual records and legal theories.

Katsas heard the arguments alongside two other judges who've been in the news recently: Chief Judge Merrick Garland, who was nominated by President Barack Obama for the U.S. Supreme Court in 2016 but denied a hearing by the Senate majority leader, and Judge Brett Kavanaugh, whose name appears on Trump's latest list of potential Supreme Court nominees.