Colleen M. Campbell is an associate in Mayer Brown’s Washington DC office and a member of the Litigation & Dispute Resolution and Supreme Court & Appellate practices. She specializes in statutory and regulatory challenges, environmental issues, and class action lawsuits. Colleen is experienced in matters involving complex statutory issues as well as in advising clients facing complex legal questions in strategic decision-making. Colleen has drafted briefs filed before the US Supreme Court, the federal courts of appeals, and multiple trial courts across the country. Among other things, her experience includes briefing constitutional issues, federal preemption questions, and complex regulatory challenges under the APA.

Maintaining a broad practice to assist clients in all stages of litigation, Colleen also has substantial experience leading discovery, working with technical experts, and taking and defending high-stakes fact witness and expert witness depositions. Colleen further has considerable experience successfully litigating the enforceability of arbitration agreements—particularly in the consumer and employment contexts—as well as briefing critical motions seeking the dismissal of class actions. In addition, Colleen has experience advising businesses in editing and drafting arbitration agreements. Colleen also advises and represents clients on legislative matters, helping prepare clients to testify before Congressional Committees and address potential legal issues in proposed legislation.

Colleen’s experience includes:

  • Advising a Fortune-100 company in high-stakes, environmental disaster litigation on issues of corporate separateness, jurisdiction, and the enforceability of adverse foreign judgments;
  • Serving as one of the counsel who crafted a Dormant Commerce Clause challenge to a California ballot initiative in an action recently granted certiorari before the United States Supreme Court;
  • Serving as part of a core trial team challenging a Rhode Island state statute as in violation of the Dormant Commerce Clause;
  • Challenging two state statutes that violated the Federal Arbitration Act.

Prior to joining Mayer Brown, Colleen clerked for the Honorable James B. Loken on the US Court of Appeals for the Eighth Circuit. Colleen graduated magna cum laude from Harvard Law School. Colleen obtained her B.A. summa cum laude from Emory University, where she was elected to Phi Beta Kappa and majored in international relations.


Emory University, BA, summa cum laude
Phi Beta Kappa

Harvard Law School, JD, magna cum laude


  • District of Columbia


  • US Court of Appeals for the First Circuit
  • US Court of Appeals for the Fourth Circuit
  • US Court of Appeals for the Seventh Circuit
  • US Court of Appeals for the Ninth Circuit
  • US Court of Appeals for the Tenth Circuit
  • US Court of Appeals for the District of Columbia Circuit
  • US District Court for the Northern District of Illinois