If Article 1, Section 6, of the Constitution [the emoluments clause] disallows Senator Clinton from serving as Secretary of State, then who has standing to sue?Well, Judicial Watch, an organization whose website the other day included the prominent headlines "Illegal Immigrant Gangs Commit Most U.S. Crime" and "Porn Part Of Job At U.S. Agency," has given me an answer! They found a State Department employee who, they argue, kinda, somehow is suffering an injury now that Ms. Clinton is Secretary of State. The argument appears to go as follows: this employee swore an oath to defend the Constitution; Ms. Clinton's service as Secretary of State violates the Constitution; therefore, the employee would be violating his oath to work for her. Furthermore, it "materially and fundamentally changes the terms of [his] employment" and "constructively discharges him" from his job, which he has a property interest in keeping.
It's a 5th Amendment (procedural due process) argument. Cue Board of Regents of State Colleges v. Roth.
Dude is seeking an injunction preventing Ms. Clinton from serving as Secretary of State, a declaration that she is constitutionally ineligible, and a couple of other things.
Dig the complaint yourself (PDF).