But it is further insisted that the treaty of 1803, between the United States and France, by which this territory was acquired, has so restrained the constitutional powers of Congress, that it cannot, by law, prohibit the introduction of slavery into that part of this territory north and west of Missouri, and north of thirty-six degrees thirty minutes north latitude. By a treaty with a foreign nation, the United States may rightfully stipulate that the Congress will or will not exercise its legislative power in some particular manner, on some particular subject. Such promises, when made, should be voluntarily kept, with the most scrupulous good faith. But that a treaty with a foreign nation can deprive the Congress of any part of the legislative power conferred by the people, so that it no longer can legislate as it was empowered by the Constitution to do, I more than doubt. The powers of the Government do and must remain unimpaired. The responsibility of the Government to a foreign nation, for the exercise of those powers, is quite another matter. That responsibility is to be met, and justified to the foreign nation, according to the requirements of the rules of public law; but never upon the assumption that the United States had parted with or restricted any power of acting according to its own free will, governed solely by its own appreciation of its duty. The second section of the fourth article is, "This Constitution, and the laws of the United States which shall be made in pursuance thereof, and all treaties made or which shall be made under the authority of the United States, shall be the supreme law of the land." This has made treaties part of our municipal law; but it has not assigned to them any particular degree of authority, nor declared that laws so enacted shall be irrepealable. No supremacy is assigned to treaties over acts of Congress. That they are not perpetual, and must be in some way repealable, all will agree. If the President and the Senate alone possess the power to repeal or modify a law found in a treaty, inasmuch as they can change or abrogate one treaty only by making another inconsistent with the first, the Government of the United States could not act at all, to that effect, without the consent of some foreign Government. I do not consider, I am not aware it has ever been considered, that the Constitution has placed our country in this helpless condition. The action of Congress in repealing the treaties with France by the act of July 7th, 1798, (1 Stat. at Large, 578,) was in conformity with these views. In the case of Taylor et al. _v._ Morton, (2 Curtis's Cir. Ct. R., 454,) I had occasion to consider this subject, and I adhere to the views there expressed.