foreign powers? To the second question it may be answered, that if the general government should interpose by virtue of this constitutional authority, it will be, of course, bound to pursue the authority. But the authority extends no further than to a guaranty of a republican form of government, which supposes a preexisting government of the form which is to be guaranteed. As long, therefore, as the existing republican forms are continued by the states, they are guaranteed by the federal Constitution. Whenever the states may choose to substitute other republican forms, they have a right to do so, and to claim the federal guaranty for the latter. The only restriction imposed on them is, that they shall not exchange republican for anti-republican Constitutions; a restriction which, it is presumed, will hardly be considered as a grievance.
A protection against invasion is due from every society to the parts composing it. The latitude of the expression here used seems to secure each state, not only against foreign hostility, but against ambitious or vindictive enterprises of its more powerful neighbors. The history, both of ancient and modern confederacies, proves that the weaker members of the union ought not to be insensible to the policy of this article.