Diane Hazel is a partner and litigation attorney with Foley & Lardner LLP. Diane is based in the firm’s Denver office, where she is a member of the firm’s Antitrust Practice Group.

Diane’s practice focuses on government investigations, antitrust counseling and litigation, and other white collar, class action, and commercial litigation matters. She has worked on a wide range of merger matters and antitrust conduct issues, including market allocation, price fixing, group boycotts, reverse payments, product hopping, refusals to deal, bundling, exclusive dealing, tying, MFNs, and joint ventures.

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’s practice also included matters in high-profile areas, with a particular focus on the technology, health care, and life sciences sectors.

Diane was previously 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.  

Thought Leadership

  • 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)


  • Recognized, 5820 Top Lawyers, Antitrust (2023)
  • 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)

Community Engagement

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

Professional Membership

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


  • Georgetown University Law Center (J.D., cum laude, 2010)
  • Wake Forest University (B.A., magna cum laude, 2005)


  • Colorado
  • Washington, D.C.