An impoundment is an executive refusal to spend funds appropriated by Congress. Although U.S. presidents historically impounded funds with some regularity, Congress curtailed this practice by statute after President Nixon abused it. As amended over time, the
Impoundment Control Act of 1974 (ICA) now limits the executive branch's authority to decline to spend or commit to spending funds that Congress has appropriated.
At the same time, other statutes do the opposite: While the ICA forbids officials from refusing to use funds in an appropriation, other laws bar them from spending, or even committing to spend, money without one. In particular, the
Anti-Deficiency Act, a law enacted in the 19th century and strengthened over time, makes such action unlawful—and sometimes even criminal.
Current law thus often catches the executive branch in a vise: Presidents can neither spend money without an appropriation nor refuse to spend funds once Congress has provided them. From both directions, Congress has reinforced its "
power of the purse"—its authority to
control the use of federal money.