Stephen J. Kastenberg

Tel 215.864.8122
Fax 215.864.9751

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.

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.

In his antitrust and competition practice, Stephen defends clients in class action litigation and other civil and regulatory matters involving collusive dealing, monopolization, price discrimination, and the intersection of antitrust and intellectual property.

In the securities area, he represents corporations and their directors and officers in securities fraud, derivative, and breach-of-duty litigation, as well as in internal or governmental investigations.

Stephen also has significant experience litigating commercial, Lanham Act, trade secret, and contract disputes, and defending clients against accusations of patent and trade secret infringement, violations of RICO, Title IX, and the Fair Labor Standards Act. 

Representative Matters

  • Nasdaq, Inc. v. Exchange Traded Managers Group et al.: lead counsel in securities contract dispute that resulted in judgment in favor of client of more than $80 million. See Nasdaq, Inc. v. Exchange Traded Managers Group et al., No. 17 civ. 8252, 2019 U.S. Dist. Lexis 220135 (S.D.N.Y. Dec. 20, 2019)
  • Served as lead counsel for NASDAQ OMX Group in numerous claims and regulatory matters arising from the commencement of trading of stock during the Facebook IPO; obtained an injunction against an exchange member seeking to assert substantial claims in arbitration against NASDAQ.
  • Served recently as lead counsel in defending a global pharmaceutical company in two unrelated 10-figure civil antitrust cases class actions asserting claims for monopolization and collusive dealing. In one matter, obtained summary judgment, affirmed on appeal, and decertification of an indirect purchaser class. In the second, resolved the case on terms favorable to the client after reducing the indirect purchase class from 50 states to four.
  • Represented corporate client in bringing and defending Lanham Act claims against or by competitors, seeking and defending against emergency injunctions and damages claims. Recent cases have involved billions of sales dollars. In one recent case, obtained a $50 million recovery for a client, mid-discovery.
  • Regularly represents companies and entrepreneurs in government and internal investigations; matters arising from derivative demand letters by shareholders; and in ownership disputes within closely held companies
  • Defended a Fortune 100 chemical manufacturing company against claims of more than $425 million by a purchaser, which arose from alleged fraud and breaches of purchase representations. Obtained a complete defense verdict at trial, affirmed on appeal to the Delaware State Supreme Court.
  • Led the defense of a real estate investment fund in the Florida federal and state courts in two class actions seeking hundreds of millions of dollars in damages, as well as in related individual actions asserting RICO and other violations. The claims were brought by thousands of property owners arising out of investments in 13 resort development projects. Obtained dismissal of the first class action, dismissal of two amended complaints in the second class action, and dismissal of three of the individual actions. None of the matters have resulted in adverse judgments.
  • Represented one of the world’s leading research universities in successfully defending against Title IX, contract, and related claims by students or faculty, including defeating two preliminary injunctions
  • Represents colleges and universities against claims, or anticipated claims, for reimbursement of tuition resulting from the need to implement remote learning curricula during the COVID-19 pandemic
  • Represented a global chemical company in a civil antitrust lawsuit in Colorado, where the company and a co-defendant were accused of conspiring to eliminate the plaintiff as a competitor in the auto refinishing market. Obtained summary judgment.
  • Represented a leading provider of cable, internet, and telephone services in a matter involving misappropriation of intellectual property. Resolved with the full return of all intellectual property at issue.
  • Represents public clients and board special litigation committees in derivative action litigation brought by stockholders, and advises clients in response to derivative action demand letters and other shareholder demands
  • Represented the estate of late rap musician Tupac Shakur and its co-administrator in two related defamation lawsuits arising from the lyrics of two songs on a Shakur platinum album. Obtained summary judgment in both cases and affirmance by the Third Circuit in the one matter proceeding through appeal.

Judicial Clerkships

Hon. Bailey Aldrich, U.S. Court of Appeals for the First Circuit, 1992-1993

Professional Activities

American Bar Association, Antitrust Section

New Jersey State Bar Association

Pennsylvania Bar Association

Philadelphia Bar Association

Ballard Spahr's Pro Bono Committee

Recognition & Accomplishments

The Legal 500 US, Antitrust - Civil litigation/class action - defense and plaintiff, 2019-2020

Chambers USA, antitrust, litigation: general commercial law (Pennsylvania), 2007-2020

The Best Lawyers in America, commercial litigation, securities litigation, 2012-2021; "Lawyer of the Year," Litigation - Securities (Philadelphia), 2020

Benchmark Litigation, "Local Litigation Star," General Commercial Litigation and Securities, 2009-2021

Philadelphia Business Journal, "Best of the Bar: Philadelphia's Top Lawyers," 2017

AV Peer Review Rating, Martindale-Hubbell


Co-author, "NCAA Scores Key Victory in Case Involving Paying Student Athletes," Philadelphia Business Journal, October 5, 2015

Co-author, "Court Rules NCAA Can Block Colleges from Paying Student-Athletes, But Allows Scholarships for 'Full Cost of Attendance'," Ballard Spahr alert, September 30, 2015

Co-author, "The Corporate Antitrust Policy—Privileged or Not?" Law360, November 7, 2014

Co-author, "Landmark Lawsuit Shapes NCAA and the Future of Student-Athlete Compensation," Philadelphia Business Journal, August 19, 2014

Profiled in The Legal Intelligencer's July 29, 2014, edition on winning the 2014 Pennsylvania Litigation Department of the Year award for General Litigation

Profiled by Law360 in its August 23, 2013, edition, in an article titled "Rainmaker Q&A: Ballard Spahr's Stephen Kastenberg"

Contributing author, Model Jury Instructions in Civil Antitrust Cases, an American Bar Association publication, current edition

Contributing author, Antitrust Law Developments, an American Bar Association publication, current edition

Recent Speaking Engagements

Speaker, "Antitrust and the New Administration: Insights Into Enforcement and Policy, and What Companies Should Do Now to Prepare," Ballard Spahr webinar, December 3, 2020

"Ascertaining Ascertainability," HarrisMartin's Antitrust Pay-for-Delay Litigation Conference, Philadelphia, PA, September 10, 2015

Faculty, HarrisMartin's Antitrust Pay-for-Delay Litigation CLE Conference, Philadelphia, September 22, 2014

Community Activities

Police Corruption Task Force, past appointee by Philadelphia Mayor Edward Rendell

Board Memberships

New Jersey Scholars Program, Member and past President

Lawyers' Committee for Civil Rights, Director and Trustee

Harvard Law School (J.D., cum laude, 1992)
Managing Editor, Harvard Journal on Legislation

Princeton University (A.B., cum laude, 1988)

New Jersey


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