Brett E. Legner

Litigation & Dispute Resolution, Supreme Court & Appellate


Brett Legner is counsel in Mayer Brown’s Chicago office and a member of the Supreme Court & Appellate Litigation practice. Prior to joining Mayer Brown, he spent 18 years as an appellate litigator with the Office of the Illinois Attorney General, including more than four years as Illinois Deputy Solicitor General. 

Brett has presented oral argument in more than 90 appeals. He has argued before the US Supreme Court, has argued more than a dozen cases before both the Illinois Supreme Court and United States Court of Appeals for the Seventh Circuit, and has argued in every district of the Appellate Court of Illinois. He has authored over 250 appellate briefs, including merits and amicus briefs filed with the US Supreme Court, and numerous briefs filed in the Illinois Supreme Court, US Courts of Appeals, and state appellate courts. He received the Supreme Court Best Brief Award from the National Association of Attorneys General on multiple occasions. At the trial court level, he has briefed and argued dispositive motions and motions seeking interlocutory injunctive relief in federal district courts as well as Illinois circuit courts. 

Brett has substantial experience litigating a wide variety of federal and state constitutional matters, including First Amendment, Second Amendment, contracts clause, and takings issues; environmental matters, including federal and state regulatory questions involving land use, remediation, and pollution control; administrative challenges under the Administrative Procedure Act and analogous state administrative regimes; federal and state election law issues; labor and employment matters, including collective bargaining, Title VII, Americans with Disabilities Act, and Age Discrimination in Employment Act cases; mass torts; class actions; antitrust actions; and public utility cases. While with the Illinois Attorney General’s office, he briefed and argued many of the most complex, high-profile, and sensitive lawsuits on behalf of the State.

Brett is also an adjunct professor at Loyola University Chicago School of Law, where he teaches courses on appellate advocacy and pre-trial litigation and has taught state constitutional law classes. He has written articles on US Supreme Court matters, Illinois constitutional law, and federal law, and has presented continuing legal education courses on topics including constitutional law, administrative law, defending federal court lawsuits, and the US Supreme Court. 



  • Northwestern University, BA, with honors
  • DePaul University College of Law, JD, with honors
    Order of the Coif


  • イリノイ州弁護士


  • US Supreme Court
  • US Court of Appeals for the Fifth Circuit
  • US Court of Appeals for the Sixth Circuit
  • US Court of Appeals for the Seventh Circuit
  • US Court of Appeals for the Eighth Circuit
  • US Court of Appeals for the Ninth Circuit
  • US Court of Appeals for the Tenth Circuit
  • US District Court for the District of Colorado