United States Constitution
PREAMBLE : We the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defence, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution
Article 4, Section 4
Text of Article 4, Section 4:
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.
The 'Travis Translation' of Article 4, Section 4:
The United States will guarantee every state a government elected by the citizens of that state, and it will protect the States from attack. The United States will also protect the states from local fighting, or riots, if the State legislatures ask for it. The Governor can ask for this protection if the legislature of that state is not meeting.