Stephen J. Kastenberg

Tel 215.864.8122
Fax 215.864.9751

Stephen J. Kastenberg focuses on complex business litigation with an emphasis on antitrust, securities, and corporate governance litigation. He has successfully defended public and private companies in federal and state lawsuits, including class actions, throughout the United States.

In his more than 20 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 they span such industry sectors as pharmaceuticals, chemicals, investments, media and technology, real estate, and financial services.

In his antitrust 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. He also has significant experience litigating commercial disputes and defending clients against accusations of patent infringement and violations of RICO, the Interstate Land Sales Full Disclosure Act, and the Fair Labor Standards Act.

Representative Matters

  • Serves as lead counsel for NASDAQ OMX Group in numerous claims and regulatory matters arising from the commencement of trading of a stock during the Facebook IPO; obtained an injunction against an exchange member seeking to assert substantial claims in arbitration against NASDAQ and partial dismissal at the motion-to-dismiss stage of class claims
  • Represented a Fortune 100 public company in In Re Sulfuric Acid Antitrust Litigation, a purported class action asserting antitrust claims against manufacturers and sellers of sulfuric acid; settled the price-fixing allegations for less than the cost of defense
  • Serves as lead counsel in defending a global pharmaceutical company in two 10-figure civil antitrust cases class actions asserting claims for monopolization and collusive dealing
  • Defended a Fortune 100 company against claims of more than $425 million by a purchaser, which arose from the alleged fraud and breaches of purchase representations; at trial, obtained a complete defense verdict that was affirmed on appeal
  • On behalf of a multinational pharmaceutical corporation, led a legal team that succeeded through motions to dismiss, a motion for summary judgment, and in class certification proceedings in narrowing the monopolization claims of an indirect purchaser class against a global pharmaceutical company from a nationwide class to four states
  • Represents a real estate investment fund in the Florida federal and state courts, defending two class actions and related individual actions asserting RICO and related violations on behalf of thousands of property owners arising out of its investments in 13 resort development projects; led the team that 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
  • Led a team in defeating or settling for nominal payments a series of class and collective actions lawsuits across the United States claiming that a large public company client was responsible for Fair Labor Standards Act violations supposedly committed by more than 100 independent contractors; the landmark summary judgment decision dismissing the client has been cited in two dozen unrelated cases
  • Represents 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 business of distributing products and equipment in the auto refinish market; obtained summary judgment, with appeal now pending
  • Represents a leading provider of cable, internet, and telephone services in pursuing a former employee for misappropriation of intellectual property
  • 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, obtaining 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

Chambers USA, antitrust, litigation: general commercial law (Pennsylvania), 2007-2019

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

Benchmark Litigation, "Local Litigation Star," General Commercial Litigation and Securities, 2009-2020

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

"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