William J. Moccia is Of Counsel in the New York office of Gibson, Dunn & Crutcher. He is a member of the firm’s Litigation Department, Appellate and Constitutional Law Practice Group, and Law Firm Defense Practice Group.
William has represented a broad range of clients in high-stakes constitutional, commercial, and appellate litigation across numerous substantive fields, including First Amendment, takings, breach of contract, civil RICO, securities fraud, commodities manipulation, and law firm defense. He practices in federal and state court and has plaintiff- and defense-side experience at both the trial and appellate levels. In addition to his extensive brief-writing experience, William has represented clients as “first chair” both in the courtroom and at depositions.
Among other representative matters, William played a leading role in two groundbreaking victories before the United States Supreme Court. First, he was the senior associate representing the plaintiff in The Roman Catholic Diocese of Brooklyn, New York v. Cuomo, a successful free exercise challenge to onerous State-imposed restrictions on in-person church attendance during the COVID-19 pandemic. That representation yielded a landmark Supreme Court decision that one commentator described as “one of the two most significant religion cases of the past 30 years.” Second, William was a senior member of the team representing a group of small New York landlords and the Rent Stabilization Association of NYC, Inc. in their constitutional challenge to New York State’s COVID-19 eviction moratorium. According to data published by Reuters, the Supreme Court’s decision granting an emergency injunction pending appeal in that case marked the first time the Court granted such relief to private litigants outside the religious liberties context since the inception of the pandemic, with nearly 100 prior applications having been denied.
William was also a core member of the litigation team that won a sweeping summary judgment victory in the Southern District of New York—unanimously affirmed on appeal—on behalf of Vista Outdoor Inc. in a case arising from an earn‑out dispute with the founders of stand-up paddleboard company Jimmy Styks.
William was included in the 2023, 2024, and 2025 editions of the Best Lawyers: Ones to Watch® in America for his work in Appellate Practice and Commercial Litigation.
William was one of two individual recipients of Gibson Dunn’s 2022 Frank Wheat Memorial Award, which honors attorneys who have “demonstrated leadership and initiative in their pro bono work, obtained significant results for their pro bono clients, and served as a source of inspiration to others.” He received the award in recognition of his successful pro bono representation of a Coast Guard veteran who had struggled for years to correct her military discharge records and secure a medical retirement based on PTSD she developed in 2001, when she was raped by her direct superior while on active duty.
Prior to joining Gibson Dunn, William served as a law clerk to the Honorable Christopher F. Droney of the United States Court of Appeals for the Second Circuit and the Honorable Edgardo Ramos of the United States District Court for the Southern District of New York.
William earned his Juris Doctor in 2012 from Yale Law School, where he was a Notes Editor on The Yale Law Journal. He received his Bachelor of Arts, summa cum laude, from Fordham University in 2009.
William is admitted to practice in the State of New York, before the United States District Courts for the Southern and Eastern Districts of New York, and before the United States Court of Appeals for the Second Circuit.
Capabilities
Credentials
Education:
- Yale University - 2012 Juris Doctor
- Fordham University - 2009 Bachelor of Arts
Admissions:
- New York Bar
Clerkships:
- US Court of Appeals, 2nd Circuit, Hon. Christopher F. Droney, 2015 - 2016
- USDC, Southern District of New York, Hon. Edgardo Ramos, 2013 - 2014