No treaty has ever been held unconstitutional in any court, federal or state, in the United States. That there are, however, limits, despite the fact that in no case has there arisen the necessity for applying them in a court of law, would appear beyond question. From the early years of the present Government to the decision of the Insular Cases in 1901, the Supreme Court has, upon frequent occasions, stated, not only in general terms, but with reference to specific matters, that there are limits to the subjects that may, by treaty, be made the supreme law of the land. In New Orleans v. United States1 speaking with reference to the succession of the United States Government to the French Government in Louisiana, the court said: "This succession did not authorize the United States to exercise prerogatives of sovereignty not consistent with the Constitution of the United States." In Pollard's Lessee v. Hagan2 the court said: "It cannot be admitted that the King of Spain could by treaty or otherwise impart to the United States any of his royal prerogatives, and much less can it be admitted that they have capacity to receive or power to exercise them." And, later on in the same opinion: "The court denies the faculty of the Federal Government to add to its powers by treaty." In the Cherokee Tobacco Case3 the opinion declares: "It need hardly be said that a treaty cannot change the Constitution, or be held valid if it be in violation of that instrument. This results from the nature and fundamental principles of our government."
1 10Pet. 662; 9 E. ed. 573. 2 3 How. 212; 11 L. ed. 565.
In De Geofroy v. Riggs4 Justice Field declares: "The treaty power, as expressed in the Constitution, is in terms unlimited except by those restraints which are found in that instrument against the action of the government or of its departments, and those arising from the nature of the government and of that of the States. It would not be contended that it extends so far as to authorize what the Constitution forbids, or a change in the character of the government or in that of one of the States, or a cession of any portion of the territory of the latter, without its consent. (Fort Leavenworth Railroad Co. v. Lowe, 114 U. S. 525, 5 Sup. Ct. Rep. 995; 29 L. ed. 264.) But with these exceptions, it is not perceived that there is any limit to the questions which can be adjusted touching any matter which is properly the subject of negotiation with a foreign country. (Ware v. Hylton, 3 Dall. 199; 1 L. ed. 568; Chirac v. Chirac, 2 Wheat, 259; 4 L. ed. 234; Hauenstein v. Lynham, 100 U. S. 483; 25 L. ed. 628; 8 Opinions Attys. Gen. 417; The People v. Gerke, 5 California 381.)"
In Downes v. Bidwell5 four of the majority justices in their opinion deny the authority of the treaty-making power to "incorporate" annexed territory into the United States. And the minority declare that "a treaty which undertook to take away what the Constitution secured, or to enlarge the federal jurisdiction, would be simply void." 6
3 11 Wall. 616; 20 L. ed. 227.
4 133 U. S. 258; 10 Sup. Ct. Rep. 295; 33 L. ed. 642.
5 182 U. S. 244; 21 Sup. Ct. Rep. 770; 45 L. ed. 1088.
These dicta of the Supreme Court that have been quoted are really obiter in that in no case was a treaty provision held void. However, the statement being so often and so positively asserted it may be taken for granted that there are constitutional limits to the treaty-making power, and that when these limits are overstepped, the courts will interpose their veto.