Hasen was a
law clerk to Judge
David R. Thompson of the
United States Court of Appeals for the Ninth Circuit from 1991 to 1992 before joining the
law firm of Horvitz & Levy LLP, in
Encino, California. In 1998 he took a position at
Loyola Law School, Los Angeles; in 2005, he was named by Loyola as the William H. Hannon Distinguished Professor of Law. He left Loyola to become a professor at the
University of California, Irvine School of Law in July 2011. In 2009, In 2013, the
National Law Journal included Hasen on its list of the "100 most influential lawyers in America." In 2022, Hasen joined the faculty at
UCLA School of Law.{{cite web|url = https://law.ucla.edu/faculty/faculty-profiles/richard-l-hasen ==Books==