The Supreme Court is scheduled to hear arguments today in a historic case that will decide if Members of Congress can be sued for discrimination under the Congressional Accountability Act. [IMGCAP(1)]

The case goes back to 2003, when former Senate staffer Brad Hanson sued then-Sen. Mark Dayton (D-Minn.), alleging the lawmaker improperly fired him after he took time off for heart surgery.

Dayton repeatedly has argued that the Constitution’s Speech or Debate Clause gives Members of Congress immunity for actions related to their official duties, which include hiring and firing of staff. It’s an argument repeatedly dismissed by Hanson, who argues the clause does not cover routine personnel decisions.

Aside from the Congressional implications, the showdown today will be unique because two sets of Senate lawyers will be pitted against one another.

Dayton is being represented by the Office of the Senate Chief Counsel for Employment.

And while the law firm Heller, Huron, Chertkof, Lerner, Simon & Salzman is serving as Hanson’s chief representation, Senate Majority Leader Harry Reid (D-Nev.) and Senate Minority Leader Mitch McConnell (R-Ky.) pushed through a resolution in March that ordered the Senate legal counsel to file a friend of the court brief for Hanson.

Hanson received additional support from Reps. Barney Frank (D-Mass.) and Christopher Shays (R-Conn.), who filed their own friend of the court brief.

— Elizabeth Brotherton