Stephen J. Hammer

Stephen Hammer is a senior associate in the Dallas office of Gibson Dunn.  He is a member of the firm’s Appellate and Constitutional Law and Administrative Law and Regulatory Practice groups.

Mr. Hammer specializes in litigating high-stakes appeals and critical motions in federal and state courts.  During October Term 2024, the U.S. Supreme Court appointed Mr. Hammer to brief and argue an immigration case involving expedited removal orders and adopted his position on a key question regarding the timing of judicial review.  Riley v. Bondi, 606 U.S. 259 (2025).  Mr. Hammer has also presented argument before the U.S. Court of Appeals for the Ninth Circuit and the Fifth Texas Court of Appeals and has been recognized multiple times as an appellate Rising Star by Super Lawyers. 

Mr. Hammer maintains an active pro bono practice focused on religious liberty issues and crime victims’ rights and serves as a vice president of the Dallas Lawyers Chapter of the Federalist Society.  He is a contributing lawyer-editor for the twelfth edition of Black’s Law Dictionary.

Representative Matters:

• Won unanimous Supreme Court decision holding that an insurer with financial responsibility for bankruptcy claims is a party in interest with a right to be heard in reorganization proceedings; team named Law360 Legal Lions of the Week.  Truck Ins. Exch. v. Kaiser Gypsum Co., 602 U.S. 268 (2024).
• Persuaded the Fifth Circuit to vacate in full the SEC’s Private Fund Advisers Rule, which would have fundamentally changed the way private funds and their advisers are regulated and cost $5.4 billion and millions of hours of employee time; team named Law360 Legal Lions of the Week and runner-up for AmLaw Litigation Daily’s Litigator of the Week.  Nat’l Ass’n of Private Fund Managers v. SEC, 103 F.4th 1097 (5th Cir. 2024).
• Persuaded the Fifth Circuit to reverse order holding the head of a major state agency in contempt and imposing $100,000 in daily fines and to reassign the case in long-running institutional-reform litigation; team received shout-out from AmLaw Litigation Daily’s Litigator of the Week.  M.D. ex rel. Stukenberg v. Abbott, 119 F.4th 373 (5th Cir. 2024).
• Convinced the First Texas Court of Appeals to grant five mandamus petitions directing trial court to dismiss billions of dollars in tort claims against power generation companies in multidistrict litigation arising out of the 2021 Texas winter storm; persuaded the Texas Supreme Court to deny mandamus review of those decisions without argument.  In re Luminant Generation Co., 711 S.W.3d 13 (Tex. App.—Houston [1st Dist.] 2023, orig. proceeding [mand. denied]).
• Successfully defended AT&T from emergency challenge to multibillion-dollar 5G wireless deployment brought by airline industry on eve of rollout.  In re Expanding Flexible Use in the 3.7 to 4.2 GHz Band, No. 18-122 (FCC).
• Persuaded Virginia trial court to grant summary judgment to Trinity Industries on $1.2 billion in claims under the Virginia Fraud Against Taxpayers Act and secured affirmance of that decision from the Virginia Court of Appeals; Commonwealth ex rel. Harman v. Trinity Indus., Inc., No. 1264-24-2 (Va. Ct. App.); won unanimous affirmance of dismissal of action against Trinity Industries under the Tennessee False Claims Act from the Tennessee Court of Appeals, State ex rel. Harman v. Trinity Indus., Inc., No. M2022-00167-COA-R3-CV (Tenn. Ct. App.); won unanimous affirmance of order denying motion to amend complaint against Trinity Industries under New Jersey False Claims Act from the New Jersey Superior Court, Appellate Division, State ex rel. Harman v. Trinity Indus., Inc., No. A-3788-21 (N.J. Super. Ct. App. Div.).
• Convinced the Fifth Circuit to affirm grant of summary judgment to Health Management Systems in False Claims Act case involving hundreds of millions of dollars in alleged damages, U.S. ex rel. Frey v. Health Mgmt. Sys., Inc., No. 24-11018 (5th Cir.); won affirmance from Fifth Circuit of award of attorneys’ fees to Health Management Systems in another False Claims Act case brought by the same relator, U.S. ex rel. Frey v. Health Mgmt. Sys., Inc., No. 25-20146 (5th Cir.).
• Won unanimous affirmance of summary judgment for State Farm from the Ninth Circuit in closely watched insurance case involving water intrusion damage to condominiums in Pacific Northwest.  Gold Creek Condo.-Phase I Ass’n of Apartment Owners v. State Farm Fire & Cas. Co., No. 22-35606 (9th Cir.).
• Preserved appellate reversal of half-billion-dollar jury verdict in trade-secrets case by persuading the Texas Supreme Court to deny review after calling for full merits briefing.  HouseCanary Analytics, Inc. v. Title Source, Inc., No. 20-0683 (Tex.).
• Persuaded the Fifth Circuit to render judgment upholding the constitutionality of Texas Justice of the Peace’s practice of allowing volunteer chaplains to perform invocations before court proceedings.  Freedom from Religion Found., Inc. v. Mack, 49 F.4th 941 (5th Cir. 2022).
• Presented argument on behalf of criminal defendant in appeal involving application of the plain hearing doctrine under the Wiretap Act.  United States v. Carey, 18-50393 (9th Cir.).

Before joining the firm, Mr. Hammer served as a law clerk to Chief Justice John G. Roberts, Jr. of the U.S. Supreme Court, Judge Gregory G. Katsas of the U.S. Court of Appeals for the D.C. Circuit, and Judge Jeffrey S. Sutton of the U.S. Court of Appeals for the Sixth Circuit.

Mr. Hammer graduated magna cum laude from Harvard Law School, where he served as a managing editor of the Harvard Journal of Law and Public Policy.  Before law school, Mr. Hammer served as an infantry officer in the 82nd Airborne Division of the United States Army.  His military decorations include the Bronze Star.  Mr. Hammer received an M.Phil. in theology from the University of Oxford, where he studied on a Rhodes scholarship.  He received an A.B. summa cum laude in classics from Princeton University and graduated as Latin salutatorian.

Mr. Hammer is a member of the Texas and District of Columbia bars.  He is admitted to practice before the U.S. Supreme Court, the U.S. Courts of Appeals for the Third, Fifth, Sixth, Seventh, Ninth, Eleventh, D.C., and Federal Circuits, and the U.S. District Courts for the Northern, Southern, and Western Districts of Texas and the Eastern District of Wisconsin.

Capabilities

• Appellate and Constitutional Law
• Administrative Law and Regulatory Practice
• False Claims Act / Qui Tam Defense

Credentials

Education:

• Harvard University - 2018 Juris Doctor
• University of Oxford - 2011 Master of Philosophy
• Princeton University - 2009 Bachelor of Arts

Admissions:

• District of Columbia Bar
• Texas Bar

Clerkships:

• US Supreme Court, Hon. John G. Roberts Jr., 2020 - 2021
• US Court of Appeals, DC Circuit, Hon. Gregory G. Katsas, 2019 - 2020
• US Court of Appeals, 6th Circuit, Hon. Jeffrey S. Sutton, 2018 - 2019