Safe, Smooth, and Great Travels, Sir!
For the benefit of Rand Paul, who is the only one of that "group" who has cited The Constitution as basis for his voting throughout the years and hasn't appeared to be a Commie Globalist like mittens, and/or SOROS-Controlled:
Article 4, Section 4 states -
The United States shall guarantee to every State in this Union a Republican Form of Government, and shall protect each of them against Invasion; and on Application of the Legislature, or of the Executive (when the Legislature cannot be convened) against domestic Violence.