Mark Leddy’s practice focuses on U.S. and European antitrust law, the analysis of competitive issues in mergers and acquisitions, and appearances before antitrust regulatory agencies and the federal courts in civil and criminal litigation.

Mark has played a critical role in many industry-transforming transactions and is recognized as a leading antitrust litigator.

Mark joined the firm as a partner in 1986 and was Managing Partner from 2011 to 2017; from 1991 to 1994, he was resident in the Brussels office.

Prior to joining the firm, Mark was with the U.S. Department of Justice for 14 years. He joined the Antitrust Division in New York in 1972, served as Chief of the Division’s Special Litigation Section in Washington, D.C., in 1978, became Deputy Director of Operations in 1981, and was named Deputy Assistant Attorney General, the highest career position in the Antitrust Division, in 1984. He also has been an adjunct professor at Georgetown Law School.

Notable Experiences

  • Citigroup in investigations by global regulators in the U.S., Europe, and Asia concerning LIBOR and other benchmark rates.

  • Asahi Kasei in its 2015 $2.2 billion acquisition of Polypore International and in its previous $2.2 billion acquisition of ZOLL Medical.

  • The Coca-Cola Company in numerous matters, including its strategic partnership with, and $2.15 billion acquisition of a 16.7% equity stake in, Monster Beverage; and in its previous $12.3 billion acquisition of its North American bottler, Coca-Cola Enterprises.

  • Asahi Glass, DHL Global Forwarding, NSK, and Whirlpool in cartel investigations and antitrust class litigation in various U.S. jurisdictions.

  • ArcelorMittal in numerous matters, including its recent $1.55 billion acquisition of ThyssenKrupp Steel USA through a joint venture with Nippon Steel & Sumitomo Metal Corporation; and in a federal antitrust class action alleging an industry-wide agreement among steel producers to reduce output.

  • 3M in various antitrust matters, including investigations and numerous transactions.

  • Google in connection with the DOJ’s investigation into an alleged anticompetitive agreement with other high-tech companies regarding hiring.

  • Grupo Bimbo, and its U.S. subsidiary, in its acquisition of Sara Lee Corporation’s North American Fresh Bakery business.

  • Otis Elevator Company and UTC in winning dismissal of antitrust claims in one of the first and most important court decisions applying the Supreme Court’s Twombly decision.

See More



  • June 21, 2018
    The Path Towards Modern EU Competition Policy: A 50+ Year Retrospective
  • April 12, 2012
    Managing Merger Control Risks in M&A Transactions, Under the New Competition Law: What to Expect in Brazil in Light of the US and European Experience

  • March 10, 2011
    IBA/European Commission Merger Regulation Conference
  • January 25, 2011
    A Brief History and Analysis of Corporate Criminal Liability in the U.S. and A Comparison to European Approaches
  • April 22, 2010
    ABA 58th Antitrust Law Spring Meeting
  • April 15-16, 2010
    Tulane’s 22nd Annual Corporate Law Institute