This section is from the book "The Constitutional Law Of The United States", by Westel Woodbury Willoughby. Also available from Amazon: Constitutional Law.
With reference to the special point at issue, the opinion says: "There is in reason, then, no room in this case to contend that Congress can destroy the liberties of the people of Porto Rico by exercising in their regard powers against freedom and justice which the Constitution has absolutely denied. There can also be no controversy as to the right of Congress to locally govern the island of Porto Rico as its wisdom may decide, and in so doing to accord only such degree of representative government as may be determined on by that body. There can also be no contention as to the authority of Congress to levy such local taxes in Porto Rico as it may choose, even although the amount of the local burden so levied be manifold more onerous than is the duty with which this case is concerned. But as the duty in question was not a local tax, since it was levied in the United States on goods coming from Porto Rico, it follows that, if that island was a part of the United States, the duty was repugnant to the Constitution, since the authority to levy an impost duty conferred by the Constitution on Congress does not, as I have conceded, include the right to lay such a burden on goods coming from one to another part of the United States. And, besides, if Porto Rico was a part of the United States the exaction was repugnant to the uniformity clause. The sole and only issue, then, is not whether Congress has taxed Porto Rico without representation - for, whether the tax was local or national, it could have been imposed although Porto Rico had no representative local government and was not represented in Congress - but is whether the particular tax in question was levied in such form as to cause it to be repugnant to the Constitution. This is to be resolved by answering the inquiry, Had Porto Rico, at the time of the passage of the act in question, been incorporated into and become an integral part of the United States?"
The opinion then examines: First, whether the United States has the constitutional power to acquire territory and hold it as appurtenant and dependent territory without " incorporating " it in itself in a constitutional sense; and, Second, whether, if it has the power, it has done so in the case of Porto Rico.3
The power to acquire and hold territory in whatever constitutional status it sees fit, is, says the opinion, an inherent power possessed by all sovereign States (citing numerous international law writers). This power is possessed by the United States. Its power to acquire territory is conceded. But, the opinion continues: "To concede to the United States the right to acquire, and to strip it of all power to protect the birthright of its citizens and to provide for the well being of the acquired territory by such enactments as may in view of its condition be essential, is, in effect, to say that the United States is helpless in the family of nations, and does not possess that authority which has at all times been treated as an incident of the right to acquire."
The assertion that it is contrary to the spirit of the Constitution to hold territories without incorporating them as integral parts of the United States this opinion declares to be based upon political and not upon judicial considerations, there being no particular provision of the Constitution upon the subject. "Conceding," says the opinion, "that the conception upon which the Constitution proceeds is that no territory, as a general rule, shall be acquired unless the territory may reasonably be expected to be worthy of statehood, the determination of when such blessing is to be bestowed is entirely a political question, and the aid of the judiciary cannot be invoked to usurp political discretion in order to save the Constitution from imaginary or real dangers." 4
3 TV decision as to Porto Rico would of course conclude the status of the other insular possessions obtained in 1809 from Spain.
4 This would hardly seem to meet the point, which is not as to the power to hold districts for an indefinite length of time in a territorial condition, but as to the power to annex territory without "incorporating" it in the United States.
Not only, then, has the United States the power to acquire and hold "appurtenant" territory, but, the opinion continues, this is the only status which may be given to annexed territory by the treaty-making power. For incorporation the consent of Congress is required. "It seems," the opinion continues, "impossible to conceive that the treaty-making power by a mere cession can incorporate an alien people into the United States without the express or implied approval of Congress. And from this it must follow that there can be no foundation for the assertion that, where the treaty-making power has inserted conditions which preclude incorporation until Congress has acted in respect thereto, such conditions are void and incorporation results in spite thereof. If the treaty-making power can absolutely, without the consent of Congress, incorporate territory, and if that power may not insert conditions against incorporation, it must follow that the treaty-making power is endowed by the Constitution with the most unlimited right, susceptible of destroying every other provision of the Constitution; that is, it may wreck our institutions. If the proposition be true, then millions of inhabitants of alien territory, if acquired by treaty, can, without the desire or consent of the people of the United States, speaking through Congress,. be immediately and irrevocably incorporated into the United States, and the whole structure of the government be overthrown. While thus aggrandizing the treaty-making power on the one hand, the construction at the same time minimizes it on the other, in that it strips that authority of any right to acquire territory upon any condition which would guard the people of the United States from the evil of immediate incorporation. The treaty-making power, then, under this contention, instead of having the symmetrical functions which belong to it from its very nature, becomes distorted, vested with the right to destroy upon the one hand, and deprived of all power to protect the government on the other.