Overview
Andrew Lyonsberg is a member of the Firm’s Supreme Court & Appellate Litigation and Government & Regulatory Litigation practices. An experienced appellate litigator, he has briefed more than one hundred appellate matters and dispositive trial-court motions and has argued before the US Courts of Appeals for the Fifth, Sixth, Seventh, and Eighth Circuits. Andrew has extensive experience with agency litigation under the Administrative Procedure Act, developing and executing legal strategies to successfully challenge regulations and other federal, state, and local government actions across a wide range of industries and areas of substantive law.
Andrew has been recognized in Best Lawyers: Ones to Watch (2023-2025) for appellate practice, and was named a Rising Star in Supreme Court and appellate litigation by The Legal 500 (2022). He has also been featured in the 2021-2024 editions of The Legal 500, with clients praising his “big-picture thinking” and “sophisticated view on how the executive branch operates.”
Andrew co-directs Yale Law School’s Supreme Court Advocacy Clinic, working with the next generation of leading lawyers to litigate cases pro bono before the Court. Prior to joining McDermott, Andrew served as a law clerk to the Honorable Kim McLane Wardlaw on the US Court of Appeals for the Ninth Circuit. While in law school, he was a forum editor of the Yale Law Journal.
Results
- Obtained vacatur of an SEC proxy-advice regulation in the Fifth Circuit on behalf of a leading national trade association
- Argued and won a Medicare-related False Claims Act appeal in the Seventh Circuit on behalf of a premier university health system
- Won a mandamus action against FDA in the US District Court for the District of Columbia, requiring the agency to adhere to statutory deadlines for drug application review
- Working through the Yale Supreme Court Advocacy Clinic, successfully petitioned for certiorari and won reversal in the Supreme Court on behalf of a pro bono immigration client, expanding federal court jurisdiction over agency decisions
- In a major ANDA appeal in the Federal Circuit, obtained reversal of a district court’s sua sponte invalidation of certain patent claims
- In the US District Court for the District of Columbia, secured vacatur of an HHS regulation that had authorized harmful insurance practices
- Argued and won a qualified immunity appeal in the Eighth Circuit for an incarcerated pro bono client
- In the US District Court for the Western District of Texas, invalidated the SEC’s unlawful attempt to rescind regulations without undergoing notice and comment rulemaking
- Argued and won a Section 1983 appeal in the Fifth Circuit in a high-profile case of police brutality
- In the California Court of Appeal, obtained reversal of adverse summary judgment decisions in a long-running employment class action
- Helped secure Supreme Court victory in a case that significantly narrowed the administrative law doctrine of Auer deference to agency interpretations
Recognitions
- The Best Lawyers in America, Ones to Watch in Appellate Practice, 2023-2025
- Legal 500 US, Rising Star in Appellate & Supreme Court Litigation, 2022; Appellate & Supreme Court Litigation, 2021-2025
- District of Columbia Courts, Capital Pro Bono Honor Roll, 2023
Community
- Yale Law School, visiting clinical lecturer in law, 2023 to present
Credentials
Education
Yale Law School, JD, 2016
Williams College, BA, magna cum laude, 2011
Admissions
District of Columbia
Maryland
Courts / Agencies
US Supreme Court
US Court of Appeals for the Second Circuit
US Court of Appeals for the Fourth Circuit
US Court of Appeals for the Fifth Circuit
US Court of Appeals for the Sixth Circuit
US Court of Appeals for the Seventh Circuit
US Court of Appeals for the Eighth Circuit
US Court of Appeals for the Ninth Circuit
US Court of Appeals for the Federal Circuit
US Court of Appeals for the District of Columbia Circuit
US District Court for the District of Columbia
US District Court for the District of Maryland
