Judicial Watch is challenging Hillary Clinton’s eligibility to serve as Secretary of State, according to The Times.

The suit is based on an obscure section of the Constitution on compensation for public officials, the emoluments clause. The clause says no member of Congress can be appointed to a government post if that job’s pay was increased during the lawmaker’s current term.

Clinton was serving in Congress when the secretary of state’s salary was raised to its current level of $191,300. So that Clinton could take the post, Congress last month lowered the salary to $186,600, the level when she began her second Senate term. A similar tactic has been used so that several other members of Congress from both parties could serve in the Cabinet.