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Peter D. Keisler


PETER D. KEISLER, a former Acting Attorney General of the United States and a co-chair of Sidley’s Supreme Court and Appellate practice, has successfully represented some of the country’s largest companies in the telecommunications, transportation, energy and healthcare industries, as well as a host of national trade associations, providing extensive insight and experience gained from his more than 25 years of private and public sector experience. Including him in its top-tier of the nation’s appellate lawyers, Chambers USA 2014 notes that clients told the directory that Peter “is one of the top appellate litigators in the country at this time. He has incredible mastery of appellate argument, and how to submit the most compelling case to federal judges.”

Peter has argued a wide range of federal constitutional, statutory, and administrative law cases. His practice representing clients before the United States Supreme Court, federal courts of appeals and federal district courts has included the leading role in the nation’s most important energy lawsuits of the past several years, including UARG v. EPA, AEP v. Connecticut, EME Homer City Generation LP v. EPA, and United States v. Cinergy Corp.

Peter's recent arguments before the U.S. Supreme Court include:

  • Utility Air Regulatory Group v. Environmental Protection Agency (UARG v. EPA). Peter successfully argued that the EPA has no authority to impose permitting obligations on a source based solely on its emissions of greenhouse gases.
  • American Electric Power Co. v. Connecticut. Peter successfully represented four utility companies in this case, in which the Court unanimously reversed the court of appeals and held that states and private parties could not seek judicially-imposed reductions in greenhouse gas emissions against electric utilities under a federal common-law nuisance theory. The leading Supreme Court blog called this litigation “the biggest-ever case on the issue of global warming” and AmLaw Media named Peter its “Appellate Lawyer of the Week” for the argument, calling the case “one of the biggest environmental cases of the decade, if not the century.” 
  • National Cable & Telecommunications Association v. Gulf Power. Peter successfully argued on behalf of the cable television industry in this case, in which the Court held that cable operators offering high-speed Internet service are entitled to access to electric utility poles at regulated rates.
  • Roberts v. Sea-Land Services, Inc. Peter successfully argued on behalf of the respondent in this case involving the construction and application of federal worker compensation laws.

Peter is widely recognized as a leader in his field. In 2012, the National Law Journal/Legal Times named Peter to its list of “Champions & Visionaries,” a select group of “attorneys whose business foresight or legal acumen has expanded their firms, advanced the law or improved government.” The NLJ noted that Peter “has been front and center in almost every major energy lawsuit in the past two years.” Since 2011, Peter has been recognized in Benchmark Litigation for his appellate practice and has also been included in the “Best Lawyers in America” directory for his appellate, commercial litigation and media law work. Law360 named Peter one of its “MVPs” for Appellate Law (2014) and Energy Law (2011). Chambers USA 2013 noted that Peter “is singled out as ‘one of the most extraordinary advocates’ for his outstanding work on behalf of clients from a wide range of industries.” Washingtonian magazine has included Peter on its 2013 list of Washington’s Best Lawyers as one of the region’s “best legal minds” for his Supreme Court practice. In 2014, Peter was featured in a Greenwire article “If the Clean Air Act’s on the docket, Keisler’s on the case.”

Peter started his career at Sidley as an associate in 1989 after completing a clerkship for Justice Anthony Kennedy. In 2002 he joined the Department of Justice (DOJ) as the Principal Deputy Associate Attorney General. Peter spent most of his more than five-year tenure at DOJ as the Assistant Attorney General for the Civil Division, and ultimately served as Acting Attorney General of the United States. He returned to Sidley in 2008.

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