Impoundment Control Act (ICA) 1974
The ICA provides specific procedures that the President can follow to reduce, delay, or eliminate certain funding in an account. The Act apportions any impoundments into two categories: rescissions and deferrals.
The invocation means Trump can redline specific areas that ‘must’ be addressed in terms of voter fraud and more. If the President wants to spend less money than Congress provides for a particular purpose, they can secure a law requiring Congressional approval to revoke the funding.