As all nations do not permit slavery, the term property, in its common and universal meaning, does not include or describe slaves. In treaties, therefore, between nations, and especially in those of the United States, whenever stipulations respecting slaves were to be made, the word "negroes," or "slaves," have been employed, and the omission of these words in this clause, increases the uncertainty whether, by the term property, slaves were intended to be included. But admitting that such was the intention of the parties, the stipulation is not only temporary, but extends no further than to the property actually possessed by the inhabitants of Missouri, when it was first occupied by the United States. Property since acquired by them, and property acquired or possessed by the new inhabitants of Missouri, has in each case been acquired under the laws of the United States, and not during and under the laws of the province of Louisiana. Should, therefore, the future introduction of slaves into Missouri be forbidden, the feelings of the citizens would soon become reconciled to their exclusion, and the inconsiderable number of slaves owned by the inhabitants at the date of the cession of Louisiana, would be emancipated or sent for sale into States where slavery exists.
It is further objected, that the article of the act of admission into the Union, by which slavery should be excluded from Missouri, would be nugatory, as the new State in virtue of its sovereignty would be at liberty to revoke its consent, and annul the article by which slavery is excluded.
Such revocation would be contrary to the obligations of good faith, which enjoins the observance of our engagements; it would be repugnant to the principles on which government itself is founded; sovereignty in every lawful government is a limited power, and can do only what it is lawful to do. Sovereigns, like individuals, are bound by their engagements, and have no moral power to break them. Treaties between nations repose on this principle. If the new State can revoke and annul an article concluded between itself and the United States, by which slavery is excluded from it, it may revoke and annul any other article of the compact; it may, for example, annul the article respecting public lands, and in virtue of its sovereignty, assume the right to tax and to sell the lands of the United States. There is yet a more satisfactory answer to this objection. The judicial power of the United States is co-extensive with their legislative power, and every question arising under the Constitution or laws of the United States, is recognizable by the judiciary thereof. Should the new State rescind any of the articles of compact contained in the act of admission into the Union, that, for example, by which slavery is excluded, and should pass a law authorizing slavery, the judiciary of the United States on proper application, would immediately deliver from bondage, any person retained as a slave in said State. And, in like manner, in all instances affecting individuals, the judiciary might be employed to defeat every attempt to violate the Constitution and laws of the United States.