According to a new report in RollCall, some of the money President Trump wants to shuffle around from other federal programs to build his wall has already been spent, and is likely to be unavailable from the sources the Trump administration has previously identified.

Despite the ‘national emergency,’ Trump will still have to seek approval from both parties for some of the money, the report notes, effectively rendering a full one-third of the funds unavailable, RollCall’s John Donnelly writes.

As a result, it may be difficult for the president to circumvent Congress, who could still stop a large part of Trump’s ’emergency’ border wall funds from being spent.

“A reprogramming request must be approved by both Republicans and Democrats on the four authorizing and appropriating panels that oversee the Pentagon,” the new report notes. “Such approval in this case is all but certain to fail. All it would take is one chairman or ranking member to say no.”

Donnelly’s story quotes Indiana Democrat Peter J. Visclosky, chairman of the House Defense Appropriations Subcommittee, who said he would turn down any request to reprogram military money to pay for a border wall.

“I am adamantly opposed to the use of any funds provided by Congress to the Department of Defense for the unauthorized construction of a wall on the Southwest border,” Visclosky said. “I and the other members of the House Appropriations Committee will carefully examine each element of the President’s proposal and the serious jurisdictional and Constitutional concerns that it raises.