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.