A partner in the Paul, Weiss Litigation Department and head of the Supreme Court & Appellate Practice, William “Willy” Jay is one of the nation’s leading appellate advocates. A former Supreme Court clerk and Assistant to the Solicitor General, Jay has delivered more than 100 oral arguments before the U.S. Supreme Court and federal and state courts of appeals, and has authored over 400 briefs across federal and state appellate courts. Jay has handled cases in every federal court of appeals. In addition to his work in appellate courts, he is regularly retained before trial to handle critical motions and steer strategy for eventual appeal.
Jay has extensive Supreme Court credentials. He has argued 19 cases before the U.S. Supreme Court, briefed more than 65 Supreme Court cases on the merits and briefed more than 150 cases at the certiorari stage. Jay also regularly counsels clients on appellate strategy at the trial level, preparing and arguing key motions and handling post-trial briefing before district courts and federal and state administrative agencies.
Jay has extensive experience in appellate cases involving intellectual property, including patent, licensing, copyright and trademark law; financial services, class actions and mass torts, administrative law, antitrust, securities litigation, and constitutional challenges to state law. He is also a prominent advocate at the Federal Circuit.
Lawdragon Honors
| Honor | Year | Practice |
|---|---|---|
| The 2027 Lawdragon 500 Leading Litigators in America | 2027 | Appellate, inc. Supreme Court |
| The 2026 Lawdragon 500 Leading Litigators in America | 2026 | Appellate, inc. Supreme Court |
Jay’s representations include:
Supreme Court
- Patent law: Representing Teva Pharmaceuticals, Jay persuaded the Supreme Court to grant certiorari and then to overturn decades of Federal Circuit precedent on patent claim construction. The Court vacated a decision that had invalidated patent protection for Teva’s blockbuster multiple sclerosis drug, Copaxone® 20mg. Teva Pharmaceuticals USA, Inc. Sandoz, Inc. (2015). Jay also won a 9-0 victory for a patent defendant in a case of first impression construing patent validity under the 2011 America Invents Act. The Court unanimously agreed with Jay’s argument that an invention is “on sale” if sold or offered for sale, regardless of whether the sale made the invention publicly available. Helsinn Healthcare S.A. v. Teva Pharmaceuticals USA, Inc. (2019). More recently, on behalf of a patent owner in the medical device industry, Jay helped persuade the Supreme Court to retain the doctrine of “assignor estoppel,” which ruled out a challenge to the company’s patents by a person who had applied for and then sold the patents in the first place. Minerva Surgical, Inc. v. Hologic, Inc. (2021).
- Trademark law: B&B Hardware, Inc. Jay persuaded the Supreme Court to grant review and hold, by a 7-2 vote, that a Trademark Trial and Appeal Board decision on likelihood of confusion can bind a federal district court. The decision overturned an adverse trial decision for Jay's client, the trademark owner. B&B Hardware, Inc. Hargis Industries, Inc. (2015).
- Environmental law: In a decades-old conservation case involving interpretation of several 150-year-old treaties, Jay represented a group of Indian tribes and successfully persuaded the Supreme Court to affirm an injunction.
Federal Courts of Appeals
- The Boeing Company and co-defendant Southwest Airlines in obtaining a complete victory in the Fifth Circuit. Jay argued the appeal for Boeing. The court reversed district court certification of four nationwide classes in a RICO class action and ordered dismissal of the case.
- National financial institutions in persuading the Seventh Circuit to affirm summary judgment in a major Fair Housing Act lawsuit brought by one of the country’s largest local governments. The court held that the plaintiff could not establish proximate cause.
- A Swiss pharmaceutical company in a precedent-setting Fourth Circuit decision concerning international discovery under 28 U.S.C. § 1782, in which the court adopted a new standard for when a foreign company can be “found in” the United States and subjected to discovery.
- Gillette in a Third Circuit appeal defending its right to bring patent infringement claims in court rather than in arbitration.
Intellectual Property Appeals
- A biotech company and government contractor in challenging a district court decision about patent liability for products produced for the federal government.
- A medical-device company in persuading the Federal Circuit to reverse a district court decision invalidating as indefinite all 40 asserted patent claims.
- An agricultural biotech company in winning Federal Circuit reversal of a jury’s adverse verdict on patent ownership and obtaining a new remedy proceeding.
- A pharmaceutical company in winning reversal of a $40 million jury verdict of patent infringement.
- A petroleum industry client in winning Federal Circuit reversal of an adverse bench-trial decision regarding the on-sale bar and vacatur of an enhanced damages award.