Article I, Section 6, Clause 1:
The Senators and Representatives shall receive a Compensation for their Services, to be ascertained by Law, and paid out of the Treasury of the United States. They shall in all Cases, except Treason, Felony and Breach of the Peace, be privileged from Arrest during their Attendance at the Session of their respective Houses and in going to and returning from the same; and for any Speech or Debate in either House, they shall not be questioned in any other Place.
With the surprise ratification of the Twenty-Seventh Amendment, 1 it is now the rule that congressional legislation
varying – decreasing or increasing – the level of legislators' pay may not take effect until an intervening election has occurred. The only real controversy likely to arise in the interpretation of the new rule is whether pay increases that result from automatic alterations in pay are subject to the same requirement or whether it is only the initial enactment of the automatic device that is covered. That is, from the founding to 1967, congressional pay was determined directly by Congress in specific legislation setting specific rates of pay. In 1967, a law was passed that created a quadrennial commission with the responsibility to propose to the President salary levels for top officials of the Government, including Members of Congress. 2 In 1975, Congress legislated to bring Members of Congress within a separate commission system authorizing the President to recommend annual increases for civil servants to maintain pay comparability with private-sector employees. 3 These devices were attacked by dissenting Members of Congress as violating the mandate of clause 1 that compensation be
ascertained by Law. However, these challenges were rejected. 4 Thereafter, prior to ratification of the Amendment, Congress, in the Ethics Reform Act of 1989, 5 altered both the pay-increase and the cost-of-living-increase provisions of law, making quadrennial pay increases effective only after an intervening congressional election and making cost-of-living increases dependent upon a specific congressional vote. A federal court of appeals panel ruled that the cost-of-living-increase provision did not violate the Twenty-Seventh Amendment, and that a challenge to the quadrennial pay raise provision was not ripe. 6