Leon B. Greenfield has an exceptionally wide breadth of experience representing clients in complex antitrust-related matters. He has represented clients in cutting edge Section 2 litigation and agency matters. He has secured antitrust clearance for major acquisitions, litigated cases in federal and state court and counseled clients on many types of antitrust issues. Mr. Greenfield also has broad experience in matters outside the antitrust area, including securities regulatory matters and litigation and complex business litigation.


Many of Mr. Greenfield's recent matters have involved complex issues relating to monopolization allegations. Mr. Greenfield's practice also includes obtaining merger clearance for transactions in a diverse range of industries, including life sciences, defense and aerospace, computer products, scientific equipment, agricultural and other chemicals, entertainment, professional services, airlines and financial services. Many of those transactions have required regulatory approval both in the United States and other countries.

Mr. Greenfield has also handled many civil non-merger competition matters, both in the United States and the European Union, and regularly counsels clients on antitrust matters. He has represented clients in a variety of securities, regulatory and litigation matters and has been involved in many litigation and major internal investigations in the defense and aerospace, securities and corporate governance areas.

Professional Activities

Mr. Greenfield is is the Editorial Board Chair of the Antitrust Law Journal. He is Co-Editorial Chair of the Section of Antitrust Law Mergers and Acquisitions, 4th edition (forthcoming). Mr. Greenfield previously served as the Editorial Board Chair of the 2009 Annual Review of Antitrust Law Developments and as a board member in 2007 and 2008.

Mr. Greenfield has taught courses on comparative competition law and international civil litigation at Georgetown University Law Center. He also speaks frequently and has participated in events such as the ABA Antitrust Section Spring Meeting, the ABA symposium on the Antitrust Modernization Commission at Mid-Course, the Penn State Law School Seminars, the IBA Antitrust Conference in Sydney, Australia, the Canadian Competition Invitational, and the British Institute of International Comparative Law's Workshops on International Cartels and Efficiencies in Merger Analysis. Mr. Greenfield also writes regularly on antitrust topics.


    • Representing Intel Corporation in matters regarding high-tech products.
    • Represented an international airline in connection with an agency investigation into alleged price fixing.
    • Representing high-tech clients in litigation concerning standard-setting proceedings and other issues relating to intellectual property.
    • Representing shipping companies in arbitration-related issues pending before the United States Supreme Court.
    • Represented BAE Systems in obtaining antitrust clearance for its $4.2 billion acquisition of United Defense.
    • Obtaining summary judgment on behalf of Regal Cinemas in litigation over alleged antitrust violations brought by a competing theatre owner.
    • Represented Witness Systems in connection with its $950 million sale to Verint Systems in the call center software industry.
    • Representing a seller in obtaining antitrust clearance in a major transaction in the computer security industry.
    • Obtained antitrust clearance for a buyer in a major transaction in the healthcare information technology sector.
    • Representing Regal Cinemas in obtaining merger clearance in various acquisitions.
    • Represented a cellular telephone component producer in an antitrust counterclaim arising from patent litigation.
    • Represented a scientific equipment manufacturer in a major acquisition.
    • Represented four Austrian banks in obtaining dismissal of antitrust claims brought by an overseas purchaser in a case alleging fixing of rates for exchanges of European currency and gaining affirmance by Second Circuit on remand from Supreme Court.
    • Secured antitrust clearance from the Federal Trade Commission for Bayer AG's $7 billion acquisition of Aventis CropScience, creating the world's second largest crop protection corporation.


  • Named a Thomson Reuters Stand-out Lawyer – independently rated and selected by clients.
  • Regularly recognized by Chambers USA Guide nationwide for being an antitrust litigation specialist.  
  • Selected by peers for inclusion in Best Lawyers in America for antitrust law in 2020–2024.
  • Recommended in the areas of antitrust litigation and merger control by The Legal 500 United States.
  • Named to the 2012–2024 Washington DC Super Lawyers lists for his work in antitrust litigation.
  • Named to the Lawdragon 500 Leading Litigators in America list.
  • Listed in the 2014 edition of Expert Guides as a leading economist in Washington DC in the area of Competition/Antitrust Law.
  • Listed as a leading competition/antitrust attorney in the 2007–2008, 2008–2009 and 2009–2010 editions of the PLC Cross-border Competition Handbook.

Insights & News


  • Education

    • JD, University of Chicago Law School, 1989

      with honors Associate Editor, University of Chicago Law Review
    • BS, Pennsylvania State University, 1986

      with honors
  • Admissions

    • District of Columbia

    • Pennsylvania (Inactive)

  • Clerkships

    • The Hon. Stanley Marcus, US District Court for the Southern District of Florida, 1989 - 1990



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