While serving at the Justice Department, Katyal argued numerous cases before the Supreme Court, including his successful defense (by an 8–1 decision) of the constitutionality of the Voting Rights Act of 1965 in "Northwest Austin v. Holder". Katyal also successfully argued in favor of the constitutionality of the Affordable Care Act and won a unanimous decision from the Supreme Court defending former Attorney General John Ashcroft against alleged abuses of civil liberties in the war on terror in "Ashcroft v. al-Kidd". Katyal is also the only head of the Solicitor General's office to argue in the Court of Appeals for the Federal Circuit.