Mayer Brown’s Environmental team offers innovative solutions to clients facing litigation, navigating enforcement concerns, implementing regulatory compliance programs or tackling issues that arise in transactions. Our global presence—frequently representing clients in cross-border disputes and transactions throughout the Americas, Asia, Europe and the Middle East—is significantly supplemented by our deep experience litigating major cases in state and federal courts across the United States and providing preeminent appellate services.


Litigation & Enforcement

  • We secured a unanimous victory for Weyerhaeuser Company in the US Supreme Court by obtaining reversal of a Fifth Circuit decision holding that the US Fish and Wildlife Service properly designated private land in Louisiana as “critical habitat” for the endangered Dusky Gopher Frog under the Endangered Species Act, even though there are no frogs on the land and radical changes would have to be made in the land before the frog could live there. The Court held that “critical habitat” must first be “habitat” for the endangered species and that the agency’s decision whether to exclude property from a critical habitat designation is reviewable in court for abuse of discretion. The Court remanded the case to the Fifth Circuit so that the lower court could apply the correct legal standards in the first instance.
  • We serve as national counsel to an American multinational corporation, in connection with hundreds of claims pending nationwide alleging personal injury, property damage and environmental harm associates with per and polyfluorinated alkyl (PFAS) substances. The claims include actions by various state attorneys general, the Aqueous Film-Forming Foam Multidistrict Litigation pending before the Honorable Richard Gergel, and numerous additional claims.
  • We successfully defended Nicor, a major natural gas supplier, against claims by the City of Evanston, Illinois, alleging that contamination caused by Nicor migrated a half-mile into the city and contaminated its water mains, putting the health of the city’s 77,000 residents at risk. The city demanded an injunction that would require Nicor to conduct a detailed study and to prepare to replace miles of aging city water mains at a cost of hundreds of millions of dollars. After a two-week trial that included more than 10 experts, a federal trial court ruled in favor of Nicor, determining that there was no evidence that the water mains were contaminated by Nicor and no evidence that the city’s water posed a risk to its residents.
  • We successfully represented 14 major industry groups in challenging the legality of the United States Environmental Protection Agency’s 2015 regulation defining “the waters of the United States” within the meaning of the Clean Water Act (CWA). We served as lead counsel and obtained certiorari over United States’ opposition, and prevailed 9-0 on the merits on issue of where challenges to EPA’s “Waters of the U.S.” rule may be litigated. The case was featured in Law360’s “Biggest Environmental Rulings of 2018.” Subsequently, on remand, we persuaded the district court that the 2015 Rule violates the Administrative Procedure Act.
  • We represent Veolia, a French transnational company, and its US subsidiary in connection with the Flint Water Crisis—one of the highest-profile cases in the United States. Veolia was hired by the city to assist with issues—other than lead—associated with the water supply. Even though governmental investigations into the cause of the crisis have identified governmental actors—not Veolia—as the source of the problem, plaintiffs have targeted Veolia. We represent Veolia against these unwarranted allegations of wrongdoing amidst a volatile political environment and successfully defended the company through a 6-month trial in federal court that resulted in a mistrial.
  • We represent Cargill with respect to a CERCLA site in Grand Island, Nebraska involving soil and groundwater contaminated with chlorinated solvents. U.S. EPA listed the site on the National Priorities List under CERCLA and initiated remedial action. Working with a team of experts, we commented on the proposed remedial action and defended the company against claims by approximately 300 residents who alleged extensive personal injuries and property damages. Plaintiffs alleged that the majority of the solvents originated from a former Cargill facility. Plaintiffs’ counsel used Erin Brockovich extensively to recruit clients and obtain favorable local publicity. After extensive expert work, including additional investigation in the field and carefully targeted fact discovery, we prevailed on summary judgment on grounds that Cargill did not cause the contamination and did not have a duty to investigate the property to discover subterranean contamination. Avila v. CNH America LLC, 2009 WL 151600 (D. Neb. 2009), reconsideration denied, 2009 WL 666386 (D. Neb. 2009). In addition, we used the summary judgment to establish that there was insufficient evidence for EPA to identify Cargill as a PRP for the site.


Law360 recognized Mayer Brown’s Environmental practice as one of its Environmental Practice Groups of the Year for four of the past five years (2022, 2021, 2019 and 2018).

The Legal 500: United States
We have been recognized as a leading Environmental litigation practice since 2008.

Chambers USA
We have been recognized as a leading Environmental practice in Illinois since 2008. 

The National Law Journal
Two partners named Energy & Environmental Trailblazers by The National Law Journal, which recognizes lawyers who “continue to make their mark in various aspects of legal work in the areas of energy and environmental law.”

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