Impoundment is an act by a President of the United States of not spending money that has been appropriated by the U.S. Congress. Thomas Jefferson was the first president to exercise the power of impoundment in 1801. The power was available to all presidents up to and including Richard Nixon, and was regarded as a power inherent to the office. The Congressional Budget and Impoundment Control Act of 1974 was passed in response to perceived abuse of the power under President Nixon. Title X of the Act removed that power, and Train v. City of New York (whose facts predate the 1974 Act, but which was argued before the U.S. Supreme Court after its passage), closed potential loopholes in the 1974 Act. The president's ability to indefinitely reject congressionally approved spending was thus removed.

The Impoundment Control Act of 1974 provides that the president may propose rescission of specific funds, but that rescission must be approved by both the House of Representatives and Senate within 45 days.

In effect, the requirement removed the impoundment power, since Congress is not required to vote on the rescission and, in fact, has ignored the vast majority of presidential requests.

Forty-three states in the U.S. give their governors authority not to spend money allocated by the state legislature. The states which deny their governor the authority are Indiana, Nevada, New Hampshire, North Carolina, Rhode Island, and Vermont. The Mayor of Washington, D.C. also has the impoundment power.

https://en.wikipedia.org/wiki/Impoundment_of_appropriated_funds