Diane Hazel


Diane Hazel, a former Federal Trade Commission lawyer and state enforcer, represents clients in government investigations, mergers and acquisitions, antitrust litigation, and other white collar, class action, and commercial litigation matters. She is a partner in the firm’s Denver office and a member of the Antitrust Practice. Diane combines her detailed knowledge of state Attorney General and federal agency practice with a practical, solutions-oriented approach to help clients achieve their business objectives while minimizing risk.

As a litigator, Diane handles some of the largest multidistrict antitrust cases across the country. She has deep class action defense experience and regularly defends clients in federal court in cases involving alleged anticompetitive conduct, including purported allegations of price fixing and market allocation. Diane has worked in a range of industries, with a particular focus on the technology, health care, life sciences, and energy sectors. Diane also maintains an active counseling and compliance practice, working closely with general counsel, executives, and legal teams to provide guidance on issues of joint ventures, potential transactions, competitor collaborations, information sharing, Hart-Scott-Rodino (HSR) Act requirements, exclusive dealing, non-competes, product pricing and bundling, product hopping, and reverse payments as well as issues involving consumer protection and alleged deceptive business practices.

Prior to joining Foley, Diane served as a First Assistant Attorney General at the Colorado Attorney General’s Office, where she was head of the Antitrust Unit. In that capacity, she supervised dozens of antitrust matters and maintained an active litigation and merger review practice. Diane also was an attorney at the U.S. Federal Trade Commission’s Bureau of Competition Health Care Division, where she investigated and prosecuted antitrust matters in the health care and pharmaceutical industries. During her tenure at the FTC, Diane was awarded a Fulbright Grant from the U.S. State Department and spent a year in Namibia working with the Namibian government on antitrust and consumer protection matters.

Awards and Recognition

  • Recognized, Law Week Colorado’s Barrister’s Best, Antitrust Lawyer (2023)
  • Recognized, 5820 Top Lawyers, Antitrust (2023-2024)
  • Recognized, Colorado Rising Stars by Super Lawyers®, Antitrust Litigation (2018, 2019)
  • Recipient, Colorado Attorney General’s Rookie of the Year Award (2021)
  • Recipient, National Association of Attorneys General, Antitrust Chair’s Writing Award (2020)


  • Colorado Bar Association
  • District of Columbia Bar
  • American Bar Association, Section of Antitrust Law
    • Co-Chair, Competition Torts Committee (2023-present)
    • Vice-Chair, State Enforcement Committee (2020-present)
    • Young Lawyer Representative, Trade, Sports & Professional Associations Committee (2018-2019)

Community Involvement

  • Washington Park Early Learning Center Board of Directors
    • President (2021-present)
    • Secretary (2020-2021)
  • Denver Zoo Leadership Council (2022-present)
  • Denver Metro Chamber of Commerce, Leadership Denver (Class of 2023)
  • AfricAid Board of Directors (2018-2021)
  • Metro Chamber Health Care Committee (2016-2019; 2022-present)
  • Colorado Women’s Bar Association LIFT Mentoring Program

Presentations and Publications

  • Co-author, “An Analysis of the “Deputization” Theory of Section 8 of the Clayton Act,” The Antitrust Source (August 2023)
  • Author, “Colorado Antitrust Reform Carries Broad State Impact,” Law360 (August 3, 2023)
  • Quoted, “New Colo. Laws Alter Health Care, Antitrust Enforcement,” Law360 (June 9, 2023)
  • Author, “DOJ Antitrust Division and HHS OIG Enter into Partnership to Increase Coordination and Enforcement in Health Care,” Health Care Law Today (Dec. 13, 2022)
  • Co-author, “How to Assess Interlocking Directorates in Antitrust Ramp-Up” (Oct. 25, 2022)
  • Author, “FTC Imposes Civil  Penalty for Faulty ‘Messenger Model’ Contracting,” Health Care Law Today (Oct. 13, 2022)
  • Panelist, “The Outlook for U.S. Antitrust,” Antitrust Texas Conference (Sept. 20, 2022)
  • Author, “FTC Releases Paper Opposing Certificates of Public Advantage for Health Care Transactions,” Health Care Law Today (Aug. 25, 2022)
  • Moderator, “Drinking from the Legislative Firehose,” American Bar Association Antitrust Spring Meeting (April 2022)
  • Panelist, “A View from the AG’s Office: Topics in Antitrust and Consumer Protection Enforcement,” Colorado Bar Association (December 16, 2021)
  • Panelist, “The Outlook for U.S. Antitrust,” Antitrust Texas Conference (September 28, 2021)
  • Moderator, “Regulation of Social Media,” Annual Rocky Mountain Intellectual Property & Technology Law Institute (June 4, 2021)
  • Moderator, Colorado Attorney General’s Office National Privacy Day Forum (January 2021)
  • Co-author, “Class Action Settlements: Res Judicata, Release, and the Identical Factual Predicate Doctrine,” Idaho Law Review, Vol. 55 (2021)
  • Co-author, “Regulated Industries – Sports,” 2018 Annual Review of Antitrust Law Developments (March 2019)
  • Panelist, “Patent Settlement Agreements: Impact on Antitrust Enforcement Demystified,” The Knowledge Group Webinar (April 13, 2016)
  • Author, “Tying Arrangements: Do Your Pricing Policies Pass Muster Under the Antitrust Laws?” U.S. Law Magazine (Fall/Winter 2016)
  • Author, “Competition in Context: The Limitations of Using Competition Law as a Vehicle for Social Policy in the Developing World,” Houston Journal of International Law (2015)
  • Author, “Litigating with class: Considering a potential framework for class actions in Namibia,” Namibia Law Journal (2014)
  • Author, “Competition Commission of South Africa Initiates Private Healthcare Market Inquiry,” International Antitrust Bulletin (ABA Section of Antitrust Law) (December 2013)
  • Author, “The Economics of Rising Poultry Prices and Dairy Shortages,” Namibia Consumer News (November 2013)
  • Panelist, “Competition in Healthcare,” 7th Annual Conference on Competition Law, Economics & Policy (September 5, 2013)
  • Co-author, “Antitrust Issues Involving Intellectual Properties,” 2012 Annual Review of Antitrust Law Developments (March 2013)
06 March 2024 Innovative Technology Insights

FTC Issues Warning on the Use of Algorithms to Recommend or Set Prices

Duffy v. Yardi Systems sets the stage for regulators to explain how they view algorithmic pricing systems in the context of antitrust laws.
05 February 2024 Article

Hart-Scott-Rodino Reporting Threshold Increases by $8.1 Million

On February 5, 2024, the Federal Trade Commission (FTC) published a Notice in the Federal Register announcing the latest annual adjustments to the reporting thresholds under the Hart-Scott-Rodino Antitrust Improvements Act of 1976.
18 January 2024 Honors and Awards

Diane Hazel Named to Law Week Colorado’s Barrister’s Best 2023 for Antitrust Law

Foley & Lardner LLP partner Diane Hazel is recognized in Law Week Colorado’s Barrister’s Best 2023 for antitrust law.
05 January 2024 Honors and Awards

Foley Partners Recognized as 2024 Top Lawyers in Denver by 5280 Magazine

Foley & Lardner LLP partners Diane Hazel, James (Jim) Miles, and Emily Weber have been named to 5280 magazine’s 2024 list of Denver Top Lawyers, the publication’s annual compilation of the best attorneys in the region.
20 December 2023 Article

DOJ and FTC Release Significantly Expanded Merger Guidelines

On December 18, 2023, the U.S. Department of Justice Antitrust Division and Federal Trade Commission released a significant revision and expansion to the federal Merger Guidelines, the document that lays out the framework for how the Agencies will analyze mergers for potential antitrust concerns.
20 November 2023 In the News

Diane Hazel Discusses Interlocking Directorates on Our Curious Amalgam Podcast

Foley & Lardner LLP partner Diane Hazel is interviewed on the American Bar Association’s Our Curious Amalgam podcast episode, “Are You on Board With Section 8? A New Era of Enforcement Against Interlocking Directorates.”