The Constitution suggests that the National Guard when repelling an invasion can even use lethal force.
CORRECTION: I think the Constitution actually says ‘militia’. Don’t want to fall into the mistake of equating the militia and the NG. However, Texans of the appropriate age who are in the Texas NG would also be members of the militia.
Yeah, that will never happen. Mexico runs America's border and the Guard or any Texas law enforcement use rubber bullets and they will probably yell "Go Back". Lost faith in America.