William Rawle, A View of the Constitution of the United States 295--304, 305--7 1829 (2d ed.)
The Union is an association of the people of republics; its preservation is calculated to depend on the preservation of those republics. The people of each pledge themselves to preserve that form of government in all. Thus each becomes responsible to the rest, that no other form of government shall prevail in it, and all are bound to preserve it in every one.
But the mere compact, without the power to enforce it, would be of little value. Now this power can be no where so properly lodged, as in the Union itself. Hence, the term guarantee, indicates that the United States are authorized to oppose, and if possible, prevent every state in the Union from relinquishing the republican form of government, and as auxiliary means, they are expressly authorized and required to employ their force on the application of the constituted authorities of each state, "to repress domestic violence." If a faction should attempt to subvert the government of a state for the purpose of destroying its republican form, the paternal power of the Union could thus be called forth to subdue it.
Yet it is not to be understood, that its interposition would be justifiable, if the people of a state should determine to retire from the Union, whether they adopted another or retained the same form of government, or if they should, with the express intention of seceding, expunge the representative system from their code, and thereby incapacitate themselves from concurring according to the mode now prescribed, in the choice of certain public officers of the United States.
The principle of representation, although certainly the wisest and best, is not essential to the being of a republic, but to continue a member of the Union, it must be preserved, and therefore the guarantee must be so construed. It depends on the state itself to retain or abolish the principle of representation, because it depends on itself whether it will continue a member of the Union. To deny this right would be inconsistent with the principle on which all our political systems are founded, which is, that the people have in all cases, a right to determine how they will be governed.
This right must be considered as an ingredient in the original composition of the general government, which, though not expressed, was mutually understood, and the doctrine heretofore presented to the reader in regard to the indefeasible nature of personal allegiance, is so far qualified in respect to allegiance to the United States. It was observed, that it was competent for a state to make a compact with its citizens, that the reciprocal obligations of protection and allegiance might cease on certain events; and it was further observed, that allegiance would necessarily cease on the dissolution of the society to which it was due.
The states, then, may wholly withdraw from the Union, but while they continue, they must retain the character of representative republics. Governments of dissimilar forms and principles cannot long maintain a binding coalition. "Greece," says Montesquieu, "was undone as soon as the king of Macedon obtained a seat in the amphyctionic council." It is probable, however, that the disproportionate force as well as the monarchical form of the new confederate had its share of influence in the event. But whether the historical fact supports the theory or not, the principle in respect to ourselves is unquestionable.
