POTUS Delegates his Powers to use the Military to Build the Wall, Using the John Mcain defense act. Military Construction Authorization Act for Fiscal Year 2019 The bill authorizes appropriations and sets forth policies regarding military construction for the Army, Navy, Air Force, defense agencies, the North Atlantic Treaty Organization Security Investment Program, and Guard and Reserve Forces facilities. https://www.congress.gov/bill/115th-congress/house-bill/5515 SUBJECT: Delegation of Authorities and Responsibilities under Section 1763 of the National Defense Authorization Act for Fiscal Year 2019 By the authority vested in me as President by the Constitution and the laws of the United States of America, including section 301 of title 3, United States Code, I hereby delegate to the Secretary of Commerce, in coordination with executive departments and agencies through the National Security Presidential Memorandum-4 process, the functions and authorities vested in the President by section 1763 of the National Defense Authorization Act for Fiscal Year 2019 (Public Law 115-232). The delegation of authorities and responsibilities in this memorandum shall apply to any provision of any future public law that are the same or substantially the same as the provision referenced in this memorandum. Here is the link to the above text which gives no other meaningful info in addition to the text contained here https://www.whitehouse.gov/presidential-actions/presidential-memorandum-secretary-commerce-2/