Diane Hazel is a nationally recognized antitrust litigator and former government enforcer who represents clients in complex litigation and high-stakes investigations. A former attorney at both the Federal Trade Commission (FTC) and the Colorado Attorney General’s Office, Diane brings deep agency insight and strategic acumen to her work defending clients in investigations by the FTC, Department of Justice, and state Attorneys General.
Diane is a trusted advocate and litigator in some of the largest antitrust class actions in the country, with extensive experience in multidistrict litigation and federal court defense. Diane regularly represents clients facing allegations of price fixing, market allocation, monopolization, and other forms of alleged anticompetitive conduct. Her litigation practice spans a range of industries, with particular depth in technology, health care, manufacturing, and energy.
Clients value Diane’s professionalism, diligence, and clear communication. She takes a practical, business-minded approach to litigation and investigations—working closely with clients to understand their goals, minimize risk, and craft creative, effective legal strategies. Diane’s background as a former enforcer allows her to anticipate agency priorities and navigate complex regulatory landscapes with confidence.
In addition to her litigation and investigations work, Diane counsels clients on consumer protection matters, including compliance with FTC rules and issues related to fees and disclosures. She also advises on antitrust aspects of joint ventures, competitor collaborations, information sharing, distribution contracts, product pricing, and mergers, including Hart-Scott-Rodino (HSR) Act filings and merger reviews.
Prior to joining Foley, Diane served as a First Assistant Attorney General at the Colorado Attorney General’s Office, where she led the Antitrust Unit and supervised dozens of investigations and merger reviews. At the FTC’s Bureau of Competition Health Care Division, she investigated and prosecuted antitrust matters in the health care and pharmaceutical sectors. Diane was also awarded a Fulbright Grant by the U.S. State Department and spent a year in Namibia working with the Namibian government on antitrust and consumer protection initiatives.
Awards and Recognition
- Recognized, Global Competition Review and Lexology Index, Future Leader – Competition (2025)
- Recognized, Law Week Colorado, Barrister’s Best, Best Antitrust Lawyer, People’s Choice (2024)
- 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)
Affiliations
- 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 (2020-2023)
- Young Lawyer Representative, Trade, Sports & Professional Associations Committee (2018-2019)
Community Involvement
- Legal Aid Foundation Board of Trustees
- Secretary (2025-present)
- Board Member (2024-present)
- Colorado Ballet Auxiliary Board of Directors (2025-present)
- Denver Zoo Leadership Council (2022-2025)
- Washington Park Early Learning Center Board of Directors
- President (2021-2024)
- Secretary (2020-2021)
- 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
- Panelist, “Defense Views on State Enforcement,“ American Bar Association Antitrust Magazine (August 27, 2025)
- Co-author, “Federal Court Applies Antitrust Standard of Per Se Illegality to ‘Algorithmic Pricing’ Case,” Innovative Technology Insights (February 3, 2025)
- Author, “FTC Announces Final Junk Fees Rule Applying to Live-Event Tickets and Short-Term Lodging,” Consumer Class Defense Counsel (January 17, 2025)
- Co-author, “FTC and DOJ Withdraw Guidelines for Collaborations Among Competitors,” Legal News Alert (January 3, 2025)
- Moderator, “Anticompetitive Conduct Is Best Determined by the FTC,” American Bar Association Antitrust Fall Forum (November 14, 2024)
- Speaker, “Non-Compete Agreements,” Colorado Bar Association Business Law Institute (September 6, 2024)
- Speaker, “The FTC Abolished Non-Competes: What That Means for Your Clients,” Colorado Bar Association (May 16, 2024)
- Co-author, “FTC Issues Warning Letters on the Use of Algorithms to Recommend or Set Prices,” Innovative Technology Insights (March 6, 2024)
- Author, “Private equity investments in physician practices draw regulatory scrutiny,” Medical Economics (August 2023)
- 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?” 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)
Federal Court Applies Antitrust Standard of Per Se Illegality to “Algorithmic Pricing” Case
Hart-Scott-Rodino Reporting Threshold Increases by US$6.9 Million
FTC Announces Final Junk Fees Rule Applying to Live-Event Tickets and Short-Term Lodging
