Gabriel Markoff


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Gabriel Markoff specializes in white collar defense work, corporate investigations, and appellate litigation. In addition, he maintains an active pro bono practice working with a national non-profit civil rights group on impact litigation designed to defend minority voting rights and advance immigrants’ rights nationwide.

In his work at O’Melveny, Gabriel has taken on leadership roles in both litigation representations and investigatory matters. He has co-authored numerous briefs and prepared advocates for oral argument in the U.S. Supreme Court and federal courts of appeals, presented oral argument in the U.S. Court of Appeals for the Ninth Circuit (winning reversal of a grant of summary judgment against O’Melveny’s client), and first-chaired dozens of witness interviews in high-profile investigations.



Bar Admissions

  • California

Court Admissions

  • US District Court, Northern District of California
  • US Court of Appeals, Fifth and Ninth Circuits


  • University of Texas, J.D., with high honors; Chancellors Honor Society; Articles Editor, Texas Law Review
  • Texas A&M University - Corpus Christi, B.S., Biology: summa cum laude

Professional Activities


  • Honorable Judge Gregg J. Costa, US District Court for the Southern District of Texas


  • Bar Association of San Francisco
  • Barristers Club


  • Arthur Andersen and the Myth of the Corporate Death Penalty, 15 University of Pennsylvania Journal of Business Law 797 (2013) 

Student Note

  • The Invisible Barrier: Issue Exhaustion as a Threat to Pluralism in Administrative Rulemaking, 90 Texas Law Review 1065 (2012) 

Litigation Experience

  • United States v. Texas (ongoing): Represents three undocumented immigrant mothers of U.S. citizens as party intervenors in the high-profile lawsuit by 26 states against the Obama Administration’s DAPA and DACA immigration initiatives
    • Led the drafting teams in authoring numerous merits briefs in the U.S. Supreme Court, U.S. Court of Appeals for the Fifth Circuit, and Southern District of Texas
    • Successfully obtained reversal of district court’s denial of intervention to O’Melveny’s clients in Texas v. United States, 805 F.3d 653 (5th Cir. 2015)
    • Prepared co-counsel for oral argument in the U.S. Supreme Court
  • Tibble v. Edison International, 135 S. Ct. 1823 (2015): Co-authored respondents’ Supreme Court merits brief and assisted oral argument preparation. Co-authored brief following remand in the Ninth Circuit, which subsequently entered judgment in favor of O’Melveny’s clients
  • Righetti v. Richman, 2016 WL 3391236 (9th Cir. June 20, 2016): Successfully presented oral argument in the Ninth Circuit, winning reversal of the district court’s grant of summary judgment against O’Melveny’s client
  • Kobach v. Election Assistance Commission, 772 F.3d 1183 (10th Cir. 2014): Part of team that obtained reversal of the district court’s injunction ordering the federal Election Assistance Commission to add a documentary proof-of-citizenship requirement to the national voter registration form
  • In confidential arbitration proceeding arising out of a corporate investigation, conducted extensive witness preparation for three testifying witnesses and second-chaired defense of two key depositions
  • Represented major corporation in complex state court class action alleging fraud in the sale of luxury properties. Drafted briefs, second-chaired a mediation that resulted in a favorable settlement for O’Melveny’s client, and conducted extensive discovery

Investigation and Compliance Experience

  • Represents a major health services provider in a multi-jurisdiction investigation. Led interview team in taking dozens of witness interviews and compiling a confidential report for submission to governmental authorities
  • Represents a major international corporation in creating and operating an antitrust compliance program in cooperation with a court-appointed compliance monitor. Assisted numerous witness interviews, managed document reviews and productions, and drafted extensive compliance protocols and related documents
  • Represents a California consumer services company in pending investigation by state law enforcement authorities. Representation includes employee interviews, overseeing extensive forensic document work, and factual and legal research and analysis