Mr. Clark is a partner of the Firm, resident in the Washington, D.C. office. He is a complex trial and appellate litigator with especially deep experience in administrative law, cutting across dozens of statutes and numerous agencies. Mr. Clark has been with the Firm since 1996, with the exception of his period of service by virtue of appointment by the Attorney General in the U.S. Department of Justice from 2001-2005. He has worked on cutting-edge cases in numerous areas of law, and argued and won the noted Massachusetts v. EPA case in the D.C. Circuit.

Mr. Clark is rated "AV preeminent" 5.0 out of 5 by Martindale Hubbell ("the highest level of professional excellence").

From 2001 to 2005, Mr. Clark was the Deputy Assistant Attorney General for the Environment and Natural Resources Division of the Justice Department. While there, he supervised the Appellate Section (50 lawyers and staff) and the Indian Resources Section (25 lawyers and staff). Also during that period, he reviewed, edited, or contributed to virtually every brief the Environment Division of the Department of Justice filed in the Courts of Appeals, including several cases of exceptional significance he personally briefed and argued. He also worked on every Supreme Court environmental or natural resource case during this same period.

Mr. Clark's practice operates at all levels — appellate litigation, trial court litigation, agency proceedings, and regulatory and litigation counseling.

Substantively, Mr. Clark has experience with antitrust, bankruptcy, communications, complex civil litigation, constitutional law, class actions, environmental, intellectual property, and labor. For instance, in the environmental area, he has extensive experience involving the Clean Air Act, Clean Water Act, NEPA, the Energy Policy and Conservation Act of 1975, and the Energy Independence and Security Act of 2007, among many others.