from Conservative Review:
Yes, the president has the authority to build the wall
Presidents are free to deploy our troops to 140 countries without congressional authorization and build all sorts of wall and infrastructure in these countries, yet we are told a president can’t take a basic defensive action to repel an invasion of our own country: the construction of a wall twice authorized and even mandated by Congress. In reality, while it would be better for Congress to explicitly fund a new wall, the president is right to leverage the debate by threatening to use power Congress has already delegated to at least begin constructing portions of the wall. Whether we agree with such delegation or not, there is no more appropriate situation in which it should be used than with our own border.
Obviously, absent congressional authorization to expend funds, the president lacks any inherent authority to spend money. Article I, Section 9 unambiguously states, “No Money shall be drawn from the Treasury, but in Consequence of Appropriations made by Law.” However, in this case Congress has explicitly authorized fencing at the border, and although it did not appropriate the funding, the president can rely on funding through a declaration of a national emergency. Whether this rises to the level of an emergency or not is the subject of a political debate that should be settled between the political branches, not the courts.
Section 2808 of the Emergencies Act of 1976 allows the secretary of defense to “undertake military construction projects” that are “not otherwise authorized by law that are necessary to support such use of the armed forces” in the event that the president declares a national emergency. A parallel statute, <33 U.S. Code § 2293, allows the secretary, during such a declared emergency, to redirect “the resources of the Department of the Army’s civil works program, including funds, personnel, and equipment, to construct or assist in the construction, operation, maintenance, and repair of authorized civil works, military construction, and civil defense projects that are essential to the national defense.”