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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 and is the vice-chair of the Environment & Natural Resources Group and a member of the Government Affairs Group. Tom works with clients seeking to successfully navigate the federal environmental rulemaking process.

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 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 currently is one of the coordinating counsel for the overall challenge to the 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.
  • Edison Electric Institute – authored 8th Circuit and 10th Circuit amicus briefs challenging EPA’s implementation of the Clean Air Act’s regional haze provisions.
  • American Fuel & Petrochemical Manufacturers Association – represent AFPM in D.C. Circuit litigation regarding EPA’s renewable fuel standards and ozone national ambient air quality standards.
  • The Chemours Company – represent Chemours in D.C. Circuit litigation regarding listing and delisting of substitutes for ozone-depleting substances.
  • 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, and Waters of the United States rule.
  • Provide counsel to automobile manufacturer and others on compliance with motor vehicle emission control regulations.
  • 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 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, 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)

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No ‘Carte Blanche’ At EPA On Downwind Air Pollution, Lawyers Say Bloomberg Law (September 22, 2020)
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What A Kavanaugh Court Means For Environmental Law E&E News (September 22, 2020)
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EPA General Counsel Leopold Returning To Private Practice InsideEPA (September 10, 2020)
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EPA Touts Winning Record, But Some Attorneys Dispute Its Numbers Bloomberg Law (August 26, 2020)
Media Mentions
The Best Lawyers in America 2021 Recognizes 46 Crowell & Moring Attorneys, Two Selected as Lawyer of the Year (Aug.20.2020)
Firm News / Announcement
"White House Updates Rules for Environmental Reviews of Federal Actions," Administrative Law Alert (July 17, 2020). Contacts: Byron R. Brown, Daniel W. Wolff, Thomas A. Lorenzen, Elizabeth B. Dawson, David Chung
Client Alert / Newsletter
Crowell & Moring Represents University of California in Suit against Department of Homeland Security over International Student Directive (Jul.16.2020)
Firm News / Announcement

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Crowell & Moring LLP is an international law firm with more than 500 lawyers representing clients in litigation and arbitration, regulatory, 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. The firm has offices in Washington, DC, New York, Los Angeles, San Francisco, Orange County, London, Brussels, and Shanghai.

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