Mullin named DHS secretary, but Incompatibility Clause bars serving while in Senate

Trump named Sen. Markwayne Mullin (R-OK) as DHS Secretary on March 5, but the Constitution's Incompatibility Clause and the Federal Vacancies Reform Act created immediate legal obstacles: a sitting senator cannot hold an executive office simultaneously, and the Vacancies Act bars senators from serving as acting department heads without first leaving the Senate. Mullin could not serve in an acting capacity until confirmed, and Oklahoma's governor would need to appoint a replacement senator. The Senate confirmed Mullin 54-45 on March 23, resolving both legal bars.