Senior Staff Reading Group: Not to Caesar but to Peter: Why the Catholic Church is a perfect society

Drawing on the Catholic Church’s self-understanding as a complete, self-sufficient (in the Aristotelian sense, “perfect”) society, Not to Caesar but to Peter explains how the Catholic Church’s claimed legal authority provides a stable basis for religious liberty in civil law. If the Church were to remember this traditional claim of her legal authority, she could improve U.S. law’s commitment to protecting religious liberty for religious institutions and communities. In so doing, the Church can both grow in American life and, by being who she truly is, respond to common misunderstandings about the proper relationship between the Catholic Church and the state that threaten her presence in public life—ranging from those who see the Church as just another social club in civil society, to those who treat the Church as an instrument of power that should be “integrated” with the state “from within.”

William J. Haun is Senior Counsel at the Becket Fund for Religious Liberty and a Nonresident Fellow at the American Enterprise Institute (AEI). His litigation experience includes serving as second-chair in a landmark Supreme Court victory for parental religious exercise in public schools, Mahmoud v. Taylor, and being a member of the U.S. Supreme Court team that prevailed 9-0 for Catholic Social Services in Fulton v. City of Philadelphia. He’s argued in multiple federal appellate courts, federal district courts, and the Supreme Court of Texas. Will is the author of Not to Caesar but to Peter: Remembering why the Catholic Church is a perfect society, to be published by Angelico Press in October 2026.

Before joining Becket and AEI, Will practiced appellate and antitrust law at two international law firms. He also served as a law clerk to Judge Janice Rogers Brown of the U.S. Court of Appeals for the D.C. Circuit and Judge Claude Hilton of the U.S. District Court for the Eastern District of Virginia.

Will often writes on constitutional law issues, including in the Harvard Journal of Law & Public Policy, the Catholic University Law Review, National Affairs, Law & Liberty, National Review Online, the Wall Street Journal, and the Washington Post. He has been interviewed in national media and is invited to speak at leading colleges, universities, and law schools on religion and self-government.

He received his J.D. from The Catholic University of America, cum laude, where he was a published member of the Law Review. He received his B.A. from American University in political science, cum laude.

Will serves as Board Vice President of an independent, K-8 classical Catholic school, Divine Mercy Academy. He is also a Board of Advisors Member of Benedictine College’s Center for Constitutional Liberty. Will is a Knight of Merit in the Sacred Military Constantinian Order of St. George.