Justice Mariano-Florentino Cuéllar began serving on the California Supreme Court in January 2015 after being nominated by Governor Jerry Brown and retained by the voters in the November 2014 statewide election. Previously he was the Stanley Morrison Professor of Law, Professor (by courtesy) of Political Science, and Director of the Freeman Spogli Institute for International Studies at Stanford University. 

A Stanford faculty member since 2001 and a fellow of the American Academy of Arts and Sciences, Cuéllar is a scholar of public law and institutions whose books and articles explore problems in administrative law and legislation, cyberlaw and artificial intelligence, criminal justice, public health, immigration, international law and security, and the history of institutions. Between 2004 and 2015, he also held leadership positions at the Freeman Spogli Institute, Stanford’s principal institution for research and education on international affairs. As Director, Cuéllar supervised twelve centers and programs focused on international security and cooperation, governance and development, health and environmental policy, and graduate and undergraduate education. He grew the Institute’s faculty, expanded Stanford’s role in nuclear security research, launched initiatives on global poverty and cyber security, and increased opportunities for student and faculty research in Africa, Asia, and Latin America.

While on leave from Stanford, Cuéllar worked at the White House as Special Assistant to the President for Justice and Regulatory Policy (2009-2010). In this capacity, he led the Domestic Policy Council staff responsible for civil and criminal justice, public health law and policy, and immigration; negotiated bipartisan public health and criminal sentencing reform legislation; and worked to enact the bipartisan repeal of the military’s Don’t Ask/Don’t Tell policy. He also led the Presidential Transition Task Force on Immigration (2008-2009), and later, co-chaired the U.S. Department of Education’s Equity and Excellence Commission (2011-2013). After joining the court, he led the California judiciary’s Language Access Task Force (2015-2019). As a Fellow of the Harvard Corporation, he is on Harvard University’s principal governing board. He also serves on the boards of the Hewlett Foundation, the American Law Institute, and Stanford’s Human-Centered Artificial Intelligence Institute, and chairs the boards of the Center for Advanced Study in the Behavioral Sciences, AI Now, and Stanford Seed. 

A naturalized U.S. citizen born in Northern Mexico, Cuéllar graduated from Calexico High School in California’s Imperial Valley. He received a B.A. from Harvard magna cum laude, a J.D. from Yale Law School, and a Ph.D. in Political Science from Stanford. He began his career at the U.S. Treasury Department and clerked for Chief Judge Mary M. Schroeder of the U.S. Court of Appeals for the Ninth Circuit. He is married to Judge Lucy H. Koh of the U.S. District Court for the Northern District of California.