Alexander Arensberg advises clients on complex litigation and regulatory compliance issues before federal and state agencies. His practice focuses on public lands and natural resource law, renewable energy development and environmental compliance. He also has extensive experience litigating challenges to administrative decision-making, drafting appellate briefs in both federal and state courts, and conducting internal investigations and compliance reviews in response to government enforcement actions.

    As a member of the firm’s Environmental, Safety & Health Practice Group, Alexander advises clients on permitting and regulatory compliance issues arising under a broad array of federal and state environmental laws, including the National Environmental Policy Act (NEPA), Clean Water Act, Federal Land Policy and Management Act, Mining Law of 1872, Mineral Leasing Acts, Oil Pollution Act, CERCLA, Endangered Species Act and National Historic Preservation Act. This work involves close coordination with federal land managers and other permitting agencies, including the Bureau of Land Management (BLM), US Forest Service (USFS), US Fish and Wildlife Service (USFWS), US Army Corps of Engineers (USACE), Environmental Protection Agency (EPA) and various state agencies.

    Alexander has successfully litigated complex cases in state and federal court, including appeals before the Eighth, Ninth, Tenth and D.C. Circuit courts of appeals. His experience includes successfully challenging agency rulemaking and permitting decisions under the federal Administrative Procedures Act and counterpart state laws. He also helps clients participate in the administrative rulemaking process and frequently drafts public comments on their behalf in response to proposed regulations and other agency actions.

    Alexander also has significant experience assisting clients to respond to government investigations and enforcement actions, including matters involving investigations by the US Securities and Exchange Commission (SEC), Department of Justice (DOJ) and State Attorneys General.

    Alexander graduated from the University of California Berkeley School of Law, where he was the senior executive editor of the Ecology Law Quarterly and received a Certificate of Specialization in Environmental Law. In 2020, Alexander was named a Rising Star by Colorado Super Lawyers.

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    • Second-chaired 16-day federal bench trial defending Fortune 200 railroad company against US$140 million CERCLA contribution claim.
    • Represent Fortune 200 company in complex environmental litigation before the D. Idaho, S.D. Mo., D. Colo., and appeals before the Eighth, Ninth and Tenth Circuits, including defending against claims brought under CERCLA, RCRA, the Clean Water Act and state common law.
    • Represent Fortune 500 mining company to defend against citizen suit challenges to permitting decisions of the US Army Corps of Engineers under Section 404 of the Clean Water Act.
    • Represent precious metals mining company before the D.C. Circuit in appeal pursuant to the Administrative Procedures Act of Department of Energy (DOE) rulemaking decision.
    • Represent specialty chemicals company in litigation related to company’s right to mine lithium from groundwater brine in Nevada, including judicial review of numerous state administrative permitting decisions.
    • Represent State Office of the Attorney General in multistate litigation before the US Supreme Court related to hazardous waste releases from abandoned mine.


    • Represent multinational mining companies on compliance and permitting matters, particularly on Western public lands. Experience includes representing gold, silver, lithium, potash, copper and iron mining companies operating on BLM and USFS land in Colorado, Nevada, New Mexico, Arizona and Minnesota on matters arising under NEPA, FLPMA, CWA, CAA, MBTA, NHPA, the General Mining Laws, the Mineral Leasing Acts and counterpart state laws.
    • Represent Fortune 500 phosphate and potash producer on federal and state permitting matters related to tailings management, public land exchanges, mine and closure plan requirements, dam safety requirements, designations of Areas of Critical Environmental Concern (ACECs) and development of resource management plans.
    • Represent iron mining company to navigate Clean Water Act Section 404 permitting process with the US Army Corps of Engineers for major tailings basin expansion.
    • Represent municipality in acquisition of federal public lands, including advising on issues arising under FLPMA and the Recreation and Public Purposes Act.
    • Experience drafting state and federal legislation, advising clients on public policy implications of legislative efforts, and participating in federal notice and comment rulemaking efforts.

    Government Investigations

    • Assisting with representation of consumer data company in an SEC financial reporting investigation, an investigation by the New York Office of the Attorney General into potential antitrust violations, and a federal consumer protection investigation.
    • Assisting with representation of US public company’s internal review into its Anti-Money Laundering (AML) controls in response to SEC investigation.
    • Assisting with representation of chairmen of the board of directors for large construction company in relation to an internal investigation by the company’s audit committee.
    • Assisting with conducting an internal investigation for public company into potential information leaks from its board of directors.
    • Assisting with conducting an internal investigation concerning US public company’s operations in China.
    • Experience managing large-scale e-discovery projects and in support of internal investigations for both national and international clients.


    • University of California at Berkeley, Boalt Hall School of Law, J.D., 2012
    • University of Colorado at Boulder, B.A., magna cum laude, Phi Beta Kappa, 2007


    • Colorado, 2012

    Memberships and Affiliations

    • Co-Vice Chair, American Bar Association, Renewable, Alternative, and Distributed Energy Resources Committee
    • Co-Vice Chair, American Bar Association, Book Publishing Board
    • Colorado Bar Association
    • American Bar Association
    • Rocky Mountain Mineral Law Foundation
    • Certificate of Specialization in Environmental Law, Berkeley Law
    • Senior Executive Editor, Ecology Law Quarterly
    • Super Lawyers Rising Star, Colorado, 2020, 2021, 2022
    • Recognized in The Best Lawyers in America 2021: Ones to Watch for Environmental Law and Land Use and Zoning Law in Denver

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    • Speaker, “How to Mine Lithium from Groundwater – The U.S. Legal Framework,” 63rd Annual Rocky Mountain Mineral Law Institute, 2017.
    • Author, “Are Migratory Birds Extending Environmental Criminal Liability,” Ecology Law Quarterly, volume 38, p. 427, 2011.

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