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Thomas A. Lorenzen

Phone: +1 202.624.2789
1001 Pennsylvania Avenue NW
Washington, DC 20004-2595

Tom Lorenzen is a partner in Crowell & Moring's Washington, D.C. office. He is the vice-chair of the firm's Environment & Natural Resources Group and a leader of its Appellate Group. He is also a member of the firm's Litigation, Government Affairs, and Administrative Law & Regulatory groups. Tom works with clients seeking to successfully navigate the federal environmental rulemaking process. He is ranked by Chambers and Partners as one of just five Band 1 U.S. practitioners in the field of climate change law.

With a decade of Justice Department experience managing the legal defense of all EPA rules, Tom has a unique ability to help clients shape environmental policy, provide vital input on proposed federal environmental regulations through written comment and direct interaction with regulators, and mount effective judicial challenges to EPA actions that adversely affect his clients' interests. Tom also helps clients ensure compliance with existing environmental regulations. In addition, he is a noted appellate lawyer who has briefed, argued, or supervised hundreds of petitions for review of EPA regulations and other final EPA actions.

While he was at the Department of Justice, Tom oversaw many of the seminal environmental cases of the last decade. These include Massachusetts v. EPA, in which the Supreme Court affirmed EPA's authority to regulate greenhouse gases under the Clean Air Act, and Entergy v. Riverkeeper, in which the Court held that EPA has discretion under the Clean Water Act to consider or decline to consider costs in determining how to regulate cooling water intake structures. In the D.C. Circuit and the other federal courts of appeals, he oversaw the government's defense in Coalition for Responsible Regulation v. EPA, in which the court upheld EPA's first suite of greenhouse gas regulations (largely upheld by the Supreme Court in Utility Air Regulatory Group v. EPA); EME Homer City Generation, L.P. v. EPA and North Carolina v. EPA, in which the court reviewed EPA's various attempts to address interstate transport of air pollutants; numerous cases challenging EPA regulations governing emissions of hazardous air pollutants; and National Cotton Council v. EPA, in which the Sixth Circuit reviewed EPA's Clean Water Act regulations governing the application of pesticides over waters of the United States.

Tom was among the small group of attorneys chosen by industry to lead the challenges to the last administration’s Clean Power Plan, was principal author of the record issues briefs filed by industry and the challenging states in that case, and argued a portion of the case to the D.C. Circuit during its marathon en banc session in September 2016. He currently serves as coordinating counsel for industry and was the principal author of one of the intervenor-respondent briefs in the recent D.C. Circuit challenges to the Affordable Clean Energy Rule that replaced the Clean Power Plan.

Tom is a frequent lecturer and commentator in print, on the internet, and on television regarding federal environmental law, climate change regulation, administrative law, federal policymaking, and effective appellate brief-writing and argument.

Representative Matters

  • National Rural Electric Cooperative Association – provide counsel on EPA's new—and existing—source power plant greenhouse gas emission standards; Tom served as one of the coordinating counsel for the overall challenge to the last Administration's Clean Power Plan, helped to obtain an extraordinary Supreme Court stay of the rule in February 2016, and argued a portion of the case before the D.C. Circuit, sitting en banc, on September 27, 2016. He currently serves as one of the coordinating counsel for industry and state intervenors supporting EPA’s Affordable Clean Energy Rule and was the principal author of one of the briefs that industry and the states filed in support of that rule.
  • Edison Electric Institute – authored 8th Circuit and 10th Circuit amicus briefs challenging EPA’s implementation of the Clean Air Act’s regional haze provisions; provides counsel regarding preservation of the Mercury and Air Toxics Standards (MATS) and general Clean Air Act and administrative law issues.
  • American Fuel & Petrochemical Manufacturers Association – represents AFPM in multiple D.C. Circuit cases regarding EPA’s renewable fuel standards and ozone national ambient air quality standards.
  • The Chemours Company – represented Chemours in D.C. Circuit litigation regarding listing and delisting of substitutes for ozone-depleting substances. In the most recent challenge to the EPA rules, Tom presented the sole oral argument in support of the rule for both industry and the Natural Resources Defense Council after the Trump administration withdrew its support for the rule.
  • Provided counsel to major telecommunications company regarding national emission standards for hazardous air pollutants emitted by reciprocating internal combustion engines.
  • Provided counsel and prepared written comments for multiple trade associations on EPA's new source performance standards for power plant greenhouse gas emissions, EPA's proposed air quality standards for ozone, EPA's appropriate-and-necessary determination for its Mercury and Air Toxics Standards, and its Waters of the United States rule.
  • Provided counsel to automobile manufacturer and others on compliance with motor vehicle emission control regulations.
  • Provides counsel to and drafted comments for a major aircraft manufacturer supporting the issuance of a domestic aircraft GHG emission standard.
  • Prepared comments for trade association on EPA’s proposed CERCLA section 108(b) financial assurance requirements.

Tom was named to the 2016 list of National Law Journal Energy & Environmental Trailblazers. He has also been recognized as a top lawyer by Chambers USA in the area of Climate Change and Environment since 2016.


  • University of California, Los Angeles, B.A. (1982)
  • Harvard Law School, J.D. (1985)


Admitted to practice: District of Columbia

Professional Activities

  • Member, Editorial Board, Trends newsletter, published by the American Bar Association, Section on Environment, Energy, and Resources (2015-present)
  • Co-Chair, American Bar Association, Science & Technology Section, GreenTech and Climate Change Committee (2017-present)
  • Steering Committee Member and Co-Chair, District of Columbia Bar, Administrative Law & Agency Practice Community (2017-present)
  • Chair, Young Lawyers Section, Bar Association of the District of Columbia (1996-97)
  • Secretary, Bar Association of the District of Columbia (1997-1999)
  • Elected Council Member, Town of Glen Echo, Maryland (2001-2003)

View More

Chambers USA 2021 Ranks 63 Crowell & Moring Lawyers and 30 Practice Areas Among Best in U.S. (May.20.2021)
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How The Supreme Court Could Rein-In Biden’s Business Agenda Chief Executive (May 11, 2021)
Media Mentions
"Climate Summit Signals Future Directions for U.S. and Global Policy Efforts," (April 30, 2021). Contacts: Amanda Shafer Berman, Robert Holleyman, Thomas A. Lorenzen, Joshua Boswell, Himamauli Das
Client Alert / Newsletter
Lack Of Major EPA Policies Signals Caution As Biden Nears 100-Day Mark InsideEPA (April 28, 2021)
Media Mentions
"Using All the Tools in the Toolbox: An Early Assessment of Reregulation and the Biden Administration," ABA 50th Spring Conference on Environmental Law (April 27, 2021). Panelist: Thomas A. Lorenzen.
The Natural Gas Flame Continues To Burn Bright POWER Magazine (April 1, 2021)
Media Mentions
Biden’s Environmental Agenda In Bull’s-Eye for Red State AGs Bloomberg Law (March 25, 2021)
Media Mentions
Biden's Green Overhaul Will Have To Clear Trump's Judiciary Law360 (March 18, 2021)
Media Mentions
Biden's Pick To Lead Enviro At DOJ Is Appellate Vet Law360 (March 16, 2021)
Media Mentions

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Crowell & Moring LLP is an international law firm with approximately 550 lawyers representing clients in litigation and arbitration, regulatory and policy, and transactional matters. The firm is internationally recognized for its representation of Fortune 500 companies in high-stakes litigation, as well as its ongoing commitment to pro bono service and diversity, equity and inclusion. The firm has offices in Brussels, Doha, London, Los Angeles, New York, Orange County, San Francisco, Shanghai, and Washington, D.C.

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