He has successfully argued three cases before the U.S. Supreme Court: Castillo v. United States, 530 U.S. 120 (2000), which upheld the right to jury trial concerning firearms types in the Branch Davidian prosecution; Printz v. United States, 521 U.S. 98 (1997), which struck down federal mandates to the states under the Brady law; and United States v. Thompson/Center Arms Co., 504 U.S. 505 (1992), which applied the rule of lenity to firearms definitions.