Two senior Senate Republicans accused President Joe Biden of violating the law by holding up border wall construction that Congress specifically approved under the Trump administration, and they are pushing a government watchdog to force the White House’s hand.

Sen. Shelley Moore Capito, the top Republican on the Senate Appropriations Subcommittee on Homeland Security, and Vice Chairman Sen. Richard Shelby of Alabama pushed Wednesday for the Government Accountability Office to intervene on the pot of money that Congress allocated for wall construction at the U.S.-Mexico border. Capito, along with 40 Republican senators, wrote GAO Comptroller Gene Dodaro in March, stating that Biden violated the Impoundment Control Act by suspending all Department of Homeland Security border wall projects without providing legal justification.