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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.

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.

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 Law School – J.D., cum laude, 1990 (Managing Editor, Law Review; Tony Patiño Fellowship)
  • Texas A&M University - B.S., Economics, magna cum laude, 1986 (Alfred Chalk Award for top economics graduate; Student Body President)

Professional Rankings and Accolades

  • Law360 MVP Award for Competition (2015)
  • National Law Journal, Trailblazers Award for M&A and Antitrust (2015)
  • Who’s Who Legal: Competition (2007-2016)
  • The Best Lawyers in America (2006-2015); Dallas Antitrust “Lawyer of the Year” (2013)
  • Chambers USA (2004-2017); Texas Antitrust: Tier 1 (2007-2017)
  • Benchmark Litigation Guide, Litigation Star – National Antitrust (2008-2015); Local Litigation Star – Texas (2010-2015)
  • Super Lawyers (2006-2015) 

Government Service

  • Deputy Director, Bureau of Competition, Federal Trade Commission, Washington, DC (2001-2003)
  • Judicial Clerk, 1990-91, Hon. Patrick E. Higginbotham, U.S. Court of Appeals for the Fifth Circuit, Dallas, Texas (1990-1991)
  • Special Assistant for State Projects, United States Senator Phil Gramm, Washington, D.C. (1986-1987)

Professional Activities

  • ABA Antitrust Section, Long-Range Planning Committee (present)
  • Adjunct Professor, Washington & Lee University, College of Law, Lexington, Virginia (1999-2004)
  • Editorial Chair, ABA ANTITRUST LAW JOURNAL (1997-2000); Senior Editor (1995-1996)
  • Editorial Board for ABA ANTITRUST Magazine (2009-2013)
  • Co-Author and Editor, Von Kalinowski, Antitrust Laws and Trade Regulation: Desk Edition (Lexis-Nexis) (1996-present)
  • Editorial Board for ABA Antitrust Law Developments treatise (2007-2008)
  • Vice-Chair, ABA Antitrust Section Sherman Act Section 2 Committee (2000-2001)
  • Vice-Chair, ABA Antitrust Section Sherman Act Section 1 Committee (2001-2004)
  • Vice-Chair, ABA Antitrust Section Federal Trade Commission Committee (2004-2007)
  • Vice-Chair, ABA Antitrust Section Economics Committee (2008-2009)
  • Chair, Antitrust Section of Dallas Bar Association (2006-2007); Vice-Chair (2004-2005); Council (2003-present)
  • Council Member, State Bar of Texas Antitrust and Business Litigation Section (2005-present)
  • Member of Steering Committee, Texas Review of Law & Politics (2004-present)
  • Member, Antitrust and Trade Regulation Advisory Board, Practising Law Institute (2001-present)

Selected Publications

  • M. Sean Royall, Ashley E. Johnson and Jason C. McKenney, Antitrust Scrutiny of Pharmaceutical “Product Hopping,” 28 ANTITRUST 1 (Fall 2013)
  • M. Sean Royall and Adam J. Di Vincenzo, When Mergers Become a Private Matter:  An Updated Antitrust Primer, 26 ANTITRUST 41 (Spring 2012)
  • M. Sean Royall and Adam Di Vincenzo, Evaluating Mergers Between Potential Competitors Under the New Horizontal Merger Guidelines, 25 ANTITRUST 33 (Fall 2010)
  • M. Sean Royall and Joshua Lipton, The Complexities of Litigating Generic Drug Exclusion Claims in the Antitrust Class Action Context, 24 ANTITRUST 22 (Spring 2010)
  • M. Sean Royall, Ashley E. Johnson & Malachi Boyuls, Change?: Merger Enforcement in the New Administration, 47 THE ADVOCATE 54 (Summer 2009)
  • M. Sean Royall, Amanda Tessar, and Adam Di Vincenzo, Deterring Patent Ambush in Standard Setting:  Lessons from Rambus and Qualcomm, 23 ANTITRUST 34 (2009)
  • M. Sean Royall and Adam Di Vincenzo, The FTC’s N-Data Consent Order:  A Missed Opportunity to Clarify Antitrust in Standard Setting, 22 ANTITRUST 83 (2008)
  • M. Sean Royall and Sarah Vollbrecht, Avoiding the Scarlet "S": The Modern Challenges of Document Preservation and Destruction, THE AMERICAN LAWYER (June 2005)
  • M. Sean Royall, The Art of Destruction, THE AMERICAN LAWYER (September 2004)
  • M. Sean Royall, Standard Setting and Exclusionary Conduct:  The Role of Antitrust in Policing Unilateral Abuses of a Standard-Setting Process, 18 ANTITRUST 44 (2004)
  • D. Bruce Hoffman & M. Sean Royall, FTC Administrative Litigation: Past, Present, and Future, 70 ANTITRUST L. J. 319 (2003)
  • M. Sean Royall & Seth M.M. Stodder, Noerr Immunity for Sponsoring Litigation:  From Burlington Northern to Baltimore Scrap, 15 ANTITRUST 47 (2001)
  • M. Sean Royall, Coping with the Antitrust Risks of Product Integration, 68 ANTITRUST L. J. 1023 (2001)
  • M. Sean Royall, Disaggregation of Antitrust Damages, 65 ANTITRUST L. J. 311 (1997)
  • M. Sean Royall, Post-Chicago Economics, 63 ANTITRUST L. J. 445 (1995)


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


  • Texas Bar