As a military facility, even if being built by contractors, the wall becomes a security zone protected by armed military guards from leftists intent on sabotage. The zone becomes the same as any military base requiring security.
Since the military zone needs protection, invaders can be detained and become subject to military law that has precedence over the civil law. Invaders can be arrested and hauled back across the border by the army that is certain there will be no Mexican military resistance.
As a military facility, even if being built by contractors, the wall becomes a security zone protected by armed military guards from leftists intent on sabotage. The zone becomes the same as any military base requiring security.
Mattis and the rest of the careerists in DOD will fight him tooth and nail on the wall. They want no dog in the wall fight.
This is why it’s so important Trump wins a second term. This is going to be a LONG WAR.