Mark W. Mosier

Mark Mosier represents clients in high-stakes, complex litigation in appellate and trial courts across the country, including the Supreme Court of the United States.

A former law clerk to Chief Justices William Rehnquist and John Roberts, Mark has represented clients in more than 60 cases before the U.S. Supreme Court, including presenting oral argument in U.S. ex rel. Polansky v. Executive Health Resources. Mark has filed briefs in many of the highest profile cases before the Court in recent terms, including the travel ban, same-sex marriage, the Affordable Care Act, partisan gerrymandering, and legislative prayer cases.

Mark also frequently represents clients in federal and state courts of appeals. These appeals have involved a wide range of legal issues. He also advises clients on litigation strategy before the case reaches the appellate stage. He works closely with the trial team to ensure that issues are properly presented and preserved for appeal and, when necessary, to develop novel legal arguments that can help shape unsettled areas of law.

Mark is also a co-founder of the ChadTough Defeat DIPG Foundation. This non-profit organization was started after his six-year-old son, Michael, passed away from DIPG, the deadliest form of childhood brain cancer. Since its founding in 2015, the foundation has funded more than $20 million for DIPG research.