Government agencies can actually 'withhold' money by spending it—as long as they're spending it to sabotage the program.
This paper identifies 'constructive impoundment,' where the executive branch technically spends every cent Congress allocated but does so in a way that ensures the program fails. It argues that the law prohibits spending any amount of money to obstruct a funded mandate, effectively making 'legal sabotage' a spending violation.
Constructive Impoundment
SSRN · 6403339
<div> This article identifies and theorizes a distinct form of executive fiscal abuse that existing enforcement practice has failed to recognize: constructive impoundment. In a constructive impoundment, the executive branch does not refuse to obligate appropriated funds outright, which would trigger the Impoundment Control Act of 1974. Instead, it formally obligates the appropriation while deploying those funds in ways designed to frustrate or nullify the very program for which Congress provided