If the President makes it clear it will be done or heads will roll it will happen along with direct statements that the US will guard its frontiers and unfortunate accidents are a minor price to pay. If some rounds land in Mexico, tough. The US did this from 1915 to 1921 on the border and fought numerous firefights with intruders and one full scale battle at Nogales. The RINOs want to constantly use this scare tactic. The authority of the President to protect the nation is virtually unlimited, all that is needed is a patriot not a lawyer or academic pushing the hammer down.
From the USMC JTF6 Investigation Report:
Cpl Torrez said that the first time he heard Cpl Banuelos explain why he shot Mr. Hernandez was when they were interviewed collectively by a psychologist. He said that Cpl Banuelos simply said that "we reacted in a military way, we moved tactically, things like that. He said that -- he did say that Hernandez was aiming in on Blood and that's why he did it. That's the first time I heard that, was when we were with the psychologist."