Also the President can declare the Drug crisis and the illegal crisis “A Clear and Present Danger to the United States” Federalize the National Guard and p[lace them on the border to secure it.
The Congress and Judiciary have no authority to stop him as he is Commander in Chief of the U.S. Military and that authority is absolute.
a lower court injunction could temporarily halt construction. But the issue of national security will move it immediately to SCOTUS (Sessions already has written the motion, I have no doubt, as immigration is his wheelhouse)