States can repel invasion with no concern for Due Process because they act under  War Power act.  Here is what Ken Cuccinelli says: They can literally just line their National Guard up — presumably with riot gear like they would if they had a civil disturbance — and turn people back at the border. Literally, you don’t have to keep them, no catch-and-release, no nothing. You just point them back across the river and let them swim for it. Maybe you have a little courtesy shuttle and drive them over … and leave them there. https://www.breitbart.com/politics/2018/10/23/exclusive-ken-cuccinelli-states-can-stop-migrant-caravan-invasion-with-constitutional-war-powers/ Article I, § 10, cl. 3 (the Compact Clause) states: No State shall, without the Consent of Congress, lay any Duty of Tonnage, keep Troops, or Ships of War in time of Peace, enter into any Agreement or Compact with another State, or with a foreign Power, or engage in War, unless actually invaded, or in such imminent Danger as will not admit of delay.