The Government Accountability Office’s top lawyer has told Congress that President Donald Trump acted unlawfully by seeking to cancel $810 million in federal funding without lawmakers’ approval, challenging a budget tactic the administration calls a “pocket rescission.” In a letter sent Tuesday to congressional leaders, GAO General Counsel Edda Emmanuelli Perez said the Constitution gives Congress control over federal spending. She argued that a president cannot make congressionally approved funds expire by withholding them past their expiration date when Congress has not rescinded them. Trump announced Friday that he would use the maneuver to cancel the funds. A pocket rescission aims to keep money from being spent long enough for its legal availability to lapse, rather than asking Congress to approve a cancellation through the ordinary rescission process. The GAO’s assessment is a significant institutional rebuke, but it is not a court ruling, and its practical effect remains uncertain. Outside groups challenged an earlier use of the tactic, but the Supreme Court issued a preliminary ruling in 2025 that they lacked standing to bring that case. The watchdog has repeatedly concluded during Trump’s second term that the administration unlawfully withheld federal funds, but it has not sued over the issue. GAO has been without a Senate-confirmed comptroller general since Gene Dodaro retired in December. Some federal judges have said the 1974 impoundment law may give GAO’s head the authority to sue on Congress’ behalf. White House budget director Russ Vought pointed to a 1975 GAO opinion, saying the watchdog had then found Congress could not reject a president’s rescission request in time to prevent funds from lapsing. That opinion recommended clarifying the law, Vought noted; Congress has not done so. Rep. Brendan Boyle of Pennsylvania, the top Democrat on the House Budget Committee, endorsed GAO’s conclusion and urged lawmakers to pass his bill to block the tactic. Sen. Jeff Merkley of Oregon, the Senate Budget Committee’s top Democrat, also said the president has no unilateral authority to cancel the funding. The dispute puts renewed focus on Congress’ ability to enforce its spending decisions when an administration withholds money. Whether the latest GAO finding leads to legislation, a lawsuit or a change in the administration’s actions remains unclear.