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T: +1 214.698.3256
F: +1 214.571.2923

Dallas Office
2100 McKinney Avenue
Suite 1100
Dallas, TX 75201-6912, USA

T: +1 202.955.8546

Washington, D.C. Office
1050 Connecticut Avenue, N.W.
Washington, DC 20036-5306, USA


M. Sean Royall is a Gibson Dunn partner focusing on antitrust and consumer protection law and co-chairs the Firm’s Antitrust and Competition Practice Group.

BTI Consulting named Mr. Royall to its 2017 BTI Client Service All-Stars List, recognizing lawyers “who truly stand out as delivering the absolute best client service.”

Law360 named Mr. Royall to its 2015 list of MVPs in Antitrust.  The list profiled those “elite attorneys whose successes in high-stakes litigation, record-breaking deals and complex global matters earned them a spot on this year’s list of MVP award winners.”  He was one of eight lawyers nationwide featured in the antitrust category and was recognized for his work representing Sanofi-Aventis in a novel FCA case and AT&T in connection with its merger with DirecTV.  National Law Journal also named him among its 2015 Mergers & Acquisitions and Antitrust Trailblazers for his involvement in many notable mergers and antitrust litigations over the past two-plus decades, and more recently, his role in the dismissal of two significant cases against Sanofi-Aventis and Allergan.

Consistently renowned as a leader in antitrust, Mr. Royall has been honored by Chambers USA: America's Leading Business Lawyers for over a decade in Texas Antitrust Tier 1 category.  He was named Antitrust “Lawyer of the Year” in Dallas by The Best Lawyers in America as well as named a Life Science Star for non IP-litigation by LMG Life Sciences and a Litigation Star by Benchmark Litigation Guide in the National Antitrust and Texas categories.  He has also been recognized by Who’s Who Legal for Competition and Super Lawyers.

Mr. Royall served as Deputy Director of the Bureau of Competition at the Federal Trade Commission in Washington, DC from 2001 through 2003 and played a key role in shaping and overseeing the agency’s antitrust enforcement agenda, both in the merger and non-merger areas.  While at the FTC, Mr. Royall acted as lead trial counsel in the agency's groundbreaking suit against computer chip designer Rambus Inc., a case involving patent-related monopolization claims and allegations of deception in the standard-setting context.  He also served as the lead lawyer in the FTC’s review of many high-profile mergers and acquisitions, including Pepsi/Quaker Oats, Pillsbury/General Mills, Monster/, and Chevron/Texaco.

Mr. Royall has spent his entire legal career – both in and outside government – litigating complex antitrust, consumer protection, intellectual property, and other commercial disputes involving a diverse range of industries, including pharmaceuticals, healthcare, computers and computer software, semiconductors, oil and gas, petrochemicals, entertainment and ticketing, gaming equipment, pet foods, food and beverages, defense, airlines, financial services, telecommunications, and avionics.   

In addition to his litigation practice, Mr. Royall regularly represents clients before the Federal Trade Commission and Department of Justice in antitrust and consumer protection matters; counsels firms on mergers and acquisitions, joint ventures, distribution arrangements, and intellectual property licenses; consults on advertising, consumer protection, and privacy/data security issues; and assists large corporations with various legal compliance matters.

Mr. Royall received his law degree from University of Chicago Law School, where he graduated cum laude in 1990.  He served as the Managing Editor of Law Review and named a Tony Patiño Fellow, a merit-based award to law students who demonstrate leadership, a commitment to public service, and outstanding academic and personal achievement. He holds a B.S. in Economics from Texas A&M University, where he graduated magna cum laude in 1986.  He received the Texas A&M Alfred Chalk Award for being the top economics graduate and was elected Student Body President.

Mr. Royall previously served as a judicial clerk to The Honorable Patrick E. Higginbotham of the U.S. Court of Appeals for the Fifth Circuit in Dallas, Texas, in 1990-91.  He also served as the Special Assistant for State Projects to United States Senator Phil Gramm in Washington, D.C. from 1986-1987.

Representative Matters

  • Counsel for AT&T in connection with the company’s successful $48 billion acquisition of DirecTV
  • Lead antitrust counsel for Allergan Inc. in ongoing federal antitrust litigation brought by Apotex Inc., a generic drug manufacturing, alleging monopolization and wrongful exclusion of generic drug competition
  • Counsel for The Williams Companies in connection with proposed $38 billion acquisition by Energy Transfer Equity LP
  • Lead counsel for Bazaarvoice Inc. in connection with DOJ investigation of compliance with final judgment in prior merger antitrust suit
  • Lead counsel for Allergan Inc. in putative antitrust class action alleging wrongful exclusion of generic drug competition (obtained complete dismissal; now on appeal)
  • Lead counsel for Facebook in connection with the company’s 2010 privacy-related consent order/settlement with Federal Trade Commission
  • Lead counsel for Sanofi-Aventis in federal court False Claims Act litigation involving prescription drug Lovenox and generic counterparts (obtained complete dismissal)
  • Lead counsel for Mary Kay in connection with federal court purported class action involving California state law fraud and unfair competition claims (obtained complete dismissal) 
  • Lead antitrust counsel for Ticketmaster in DOJ investigation of successful $2.5 billion merger with Live Nation
  • Lead counsel for Sanofi-Aventis in federal antitrust litigation with generic drug companies involving patent-related antitrust claims (obtained full dismissal)
  • Lead counsel for Biovail Corp. in federal and state antitrust class action lawsuits alleging patent-related monopolization and conspiracy claims relating to branded pharmaceutical Wellbutrin XL
  • Lead counsel for Novo-Nordisk in federal class action antitrust suit asserting patent-related monopolization claims
  • Lead counsel for ValueClick in FTC consumer protection investigations involving various privacy and online advertising issues
  • Lead antitrust counsel for relating to the company’s successful acquisition of
  • Lead counsel for Fortune 50 company in multiple FTC consumer protection investigations involving online advertising, privacy, data security, identity theft, and telemarketing issues
  • Lead counsel for Johnson & Johnson in federal court class action antitrust (monopolization) suits involving branded pharmaceutical Ditropan XL (obtained full dismissal)
  • Lead antitrust counsel for Watson Wyatt in DOJ investigation of successful $3.5 billion merger with Towers Perrin
  • Lead antitrust counsel for United Defense in DOJ investigation of BAe's successful $4.2 billion acquisition of UDI
  • Lead antitrust counsel for Allergan in FTC investigation of successful $3.2 billion acquisition of Inamed Corp.
  • Lead antitrust counsel for Endocare, Inc. in FTC investigation of proposed merger with Galil Medical, Ltd.
  • Lead antitrust counsel for Diedrich Coffee in FTC investigation of successful merger with Green Mountain Coffee Roasters
  • Lead antitrust counsel for BMC Software in Texas state court trade secret misappropriation and monopolization suit
  • Lead counsel for Phillips Petroleum in federal court antitrust class action involving allegations of unlawful salary information exchanges among competitors
  • Lead antitrust counsel for First Reserve Corp. and Dresser Inc. in DOJ investigation of Cooper-Cameron's successful $225 million acquisition of the Dresser's Flow Control business unit
  • Lead antitrust counsel for St. Jude Medical in its successful $272 million acquisition of Endocardial Solutions Inc.
  • Lead antitrust counsel for Paramount Petroleum in FTC investigation of Alon USA Energy, Inc.’s successful $407 million acquisition of Paramount 
  • Represented Atlantic Coast Airlines in successful antitrust defense to attempted hostile takeover by Mesa Airlines

Other representative clients for Mr. Royall include 3M Company, Myspace, eBay, Frito-Lay, Sony, Dell, PepsiCo, Sempra Energy, Weight Watchers, and Tenet Healthcare.


  • University of Chicago - 1990 - Juris Doctor
  • Texas A&M University - 1986 - Bachelor of Science


  • Texas Bar

Recent Publications