Antitrust
Stephen Kastenberg of Ballard Spahr LLP is a go-to litigator for Fortune 500s and major institutions navigating high-stakes, high-profile disputes. A trusted advisor to Comcast, GlaxoSmithKline, Nasdaq, and Princeton, he leads on complex antitrust, patent, and governance matters across jurisdictions. Recently, he spearheaded Nasdaq’s defense in a closely watched SEC-related funding battle. Known for strategic insight and long-term client partnerships, Kastenberg is a standout practitioner in sophisticated commercial litigation.
Legal 500 Editorial commentary
Accolades
Philadelphia Elite
Mentions
Profile
Work Department
Litigation
Position
Partner
Career
Stephen J. Kastenberg focuses on complex business litigation with an emphasis on antitrust and competition, securities, and corporate governance litigation. He has successfully defended public and private companies and universities in federal and state lawsuits, including class actions, throughout the United States. He also regularly represents clients as plaintiffs in business disputes, or assists them through internal investigations. Stephen is based in Philadelphia and is a member of the firm’s Elected and Expanded Boards.
In his nearly 30 years of litigation experience, Stephen has achieved a significant number of victories through trial, arbitration, summary judgment, advantageous settlement, and on appeal. His clients range from Fortune 100 multinational corporations to privately held companies and nonprofit organizations, and span such industry sectors as pharmaceuticals, chemicals, investments, media and technology, real estate, financial services, and higher education.
Admissions
New Jersey
Pennsylvania
Supreme Court of New Jersey
Supreme Court of Pennsylvania
U.S. District Court for the Eastern District of Pennsylvania
U.S. Court of Appeals for the Second Circuit
U.S. Court of Appeals for the Third Circuit
U.S. Court of Appeals for the Fourth Circuit
U.S. Court of Appeals for the Ninth Circuit
U.S. Court of Appeals for the Tenth Circuit
U.S. Court of Appeals for the Eleventh Circuit
Memberships
American Bar Association, Antitrust Section
New Jersey State Bar Association
Pennsylvania Bar Association
Philadelphia Bar Association
Ballard Spahr's Pro Bono Committee
New Jersey Scholars Program, Member and past President
Lawyers' Committee for Civil Rights, Director and Trustee
Police Corruption Task Force, past appointee by Philadelphia Mayor Edward Rendell
Education
Harvard Law School (J.D., cum laude, 1992)
Managing Editor, Harvard Journal on Legislation
Princeton University (A.B., cum laude, 1988)
Content supplied by Ballard Spahr LLP
Key clients
- Comcast Corporation
- Nasdaq, Inc.
- GlaxoSmithKline LLC
- Princeton University
- Haleon, Inc.
- Lubert Adler Partners, L.P.
- American Society of Mechanical Engineers
- SC Gaming OpCo LLC (Ira Lubert gaming interests)
Work highlights
Representing Nasdaq in litigation challenging the SEC’s funding model for the Consolidated Audit Trail (CAT).