2 U.S. Code § 4574
2 U.S. Code § 4574 is about Limit on rate of compensation of Senate officers and employees. It is under Part A (Amount and Type) of Subchapter III (Senate) of Chapter 45 (Congressional Pay and Benefits) of Title 2 (The Congress) of the Code.
No officer or employee of the Senate shall receive pay for any services performed by him at any rate higher than that provided for the office or employment to which he has been regularly appointed.