Leah Brannon’s practice focuses on antitrust matters, including litigation, merger review, and government investigations.

Her work has involved cases in both federal and state courts, and she has advised clients in investigations by the U.S. Department of Justice, the Federal Trade Commission, state antitrust authorities and the European Commission.

Leah has helped to secure critical wins for clients in numerous cases, including monopolization and conspiracy litigation. She has also helped clients obtain global merger clearance in complex transactions and has guided clients through government conduct investigations.

She is also active in the firm’s pro bono practice. Her work for the firm’s pro bono clients includes filing an amicus brief on behalf of the Domestic Violence Legal Empowerment and Appeals Project in a case that led to a significant victory in the D.C. Court of Appeals for victims of sexual assault.

Leah joined the firm in 2003 and became a partner in 2008.

Notable Experiences

Antitrust Litigation

  • Keurig in monopolization litigation brought by competitors and purported class action plaintiffs, including successfully defending against a preliminary injunction seeking to block the launch of Keurig’s 2.0 coffee brewer. Successfully defended this victory on appeal, including arguing the case before the Second Circuit, which affirmed the decision below.

  • Teladoc in winning a landmark preliminary injunction against the Texas Medical Board, in a case challenging the board’s actions to restrict competition.

  • Sanofi US in winning summary judgment in a multi-billion-dollar lawsuit brought by a competitor challenging Sanofi US’s loyalty discounts for its anticoagulant drug, Lovenox and successfully defending this win on appeal to the Third Circuit.

  • Gilead Sciences in winning dismissal on all counts of a purported class action alleging unfair competition and Affordable Care Act violations.

  • Genting New York and Kien Huat Realty in winning complete dismissal of complaint alleging conspiracy and monopolization claims, and successfully defending this decision in the Second Circuit, which affirmed on all counts.

  • Whirlpool, Asahi Glass, HSBC, and others in various class actions alleging antitrust violations.

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Merger Review

  • Alstom in its €4.4 billion acquisition of Bombardier Transportation, including obtaining unconditional clearance following a second request by the DOJ.

  • Google in numerous transactions, including its $2.1 billion acquisition of Fitbit, its $12.5 billion acquisition of Motorola Mobility, its subsequent $2.91 billion sale of Motorola’s mobile devices business to Lenovo, and its previous acquisitions of Admeld, AdMob, and DoubleClick.

  • IMS Health in its $17.6 billion merger of equals with Quintiles, its €385 million acquisition of certain Cegedim information solutions and CRM businesses and its acquisition of SDI.

  • Royal DSM in its CAD 540 million all-cash acquisition of Ocean Nutrition Canada.

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Non-Merger Investigations

  • W.L. Gore & Associates in obtaining the closure (with no action taken) of an FTC investigation into whether Gore’s business practices restricted competition in waterproof and breathable fabrics in violation of Section 5 of the FTC Act.

  • Google in connection with the Department of Justice’s investigation into alleged bilateral “no cold calling” agreements, resulting in a consent decree under which the company admitted no wrongdoing.

  • A technology company in obtaining the closure (with no action taken) of a non-public FTC investigation into the company’s business practices.

  • A software vendor in the healthcare industry in obtaining the closure (with no action taken) of a non-public FTC investigation into the company’s business practices.

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Selected Activities

  • Co-Chair, Comments and Policy Committee, American Bar Association, 2021-Present
  • Council Member, Section of Antitrust Law, American Bar Association, 2017-2020
  • Senior Editor, Antitrust Law Journal, American Bar Association, 2016-2017
  • Adjunct Professor, Georgetown University, 2000
  • Teaching Fellow, Harvard University, 1998-1999
  • Fulbright Scholar (Egypt), 1996-1997


Litigating the Facts,” co-authored with David Gelfand and Gabriel Lazarus, The Antitrust Source (2024)

FTC & DOJ Propose Radical Changes to Merger Guidelines,” Cleary Gottlieb Alert Memorandum (2023)

Sweeping Changes to Premerger (HSR) Process in the United States Proposed by Enforcement Agencies,” Cleary Gottlieb Alert Memorandum (2023) 

U.S. DOJ and FTC Announce Plan to Revamp Merger Guidelines,” Cleary Gottlieb Alert Memorandum (2022) 

The ‘Twenty-First Century Antitrust Act’ Raises the Risks of Doing Business in New York,” Cleary Gottlieb Alert Memorandum (2021) 

Roundtable: The Legacy of the Microsoft Case,” Antitrust, Vol. 35, No. 2, Spring (2021) 

What to Expect From the Biden Administration,” Cleary Gottlieb Alert Memorandum (2020) 

U.S. Agencies Publish Final Revised Vertical Merger Guidelines,” Cleary Gottlieb Alert Memorandum (2020)

Avoiding or Defeating Potential Antitrust and Other Civil Suits Relating to Anti-Price Gouging Laws,” Cleary Gottlieb Alert Memorandum (2020)

‘Exploitative’ Abuse of Dominance and ‘Price Gouging’ in Times of Crisis,” Cleary Gottlieb Alert Memorandum (2020); republished by Concurrences

Antitrust Law Developments, Eighth Edition (Joint Ventures chapter), ABA (2017)

A Primer on Litigating the Fix,” co-authored with David Gelfand, Antitrust Law Journal, (2016)

Market Definition and Competitive Effects in Merger Review: The Staples-Office Depot ExampleThe Antitrust Counselor (2016)

“The Revised U.S. Horizontal Merger Guidelines and Market Definition: Early Returns,” Concurrences Competition Law Journal (2012)

“The Revised U.S. Horizontal Merger Guidelines: Can the Courts Be Persuaded?” The Antitrust Source (2010)

The Public Competition Enforcement Review (USA chapter), Law Business Research (2009)

“Antitrust Decisions of the Supreme Court, 1967-2007,” co-authored with Douglas H. Ginsburg, Competition Policy International, Vol. 3, No. 2, Autumn 2007

“Determinants of Private Antitrust Enforcement in the United States,” co-authored with Douglas H. Ginsburg, Competition Policy International, Vol. 1, No. 2, Autumn 2005