It may with truth be affirmed, that since the establishment of the several communities now constituting the States of this Confederacy, there never has been submitted to any tribunal within its limits questions surpassing in importance those now claiming the consideration of this court. Indeed it is difficult to imagine, in connection with the systems of polity peculiar to the United States, a conjuncture of graver import than that must be, within which it is aimed to comprise, and to control, not only the faculties and practical operation appropriate to the American Confederacy as such, but also the rights and powers of its separate and independent members, with reference alike to their internal and domestic authority and interests, and the relations they sustain to their confederates. To my mind it is evident, that nothing less than the ambitious and far-reaching pretension to compass these objects of vital concern, is either directly essayed or necessarily implied in the positions attempted in the argument for the plaintiff in error. How far these positions have any foundation in the nature of the rights and relations of separate, equal, and independent Governments, or in the provisions of our own Federal compact, or the laws enacted under and in pursuance of the authority of that compact, will be presently investigated. In order correctly to comprehend the tendency and force of those positions, it is proper here succinctly to advert to the facts upon which the questions of law propounded in the argument have arisen. This was an action of trespass _vi et armis_, instituted in the Circuit Court of the United States for the district of Missouri, in the name of the plaintiff in error, _a negro_ held as a slave, for the recovery of freedom for himself, his wife, and two children, _also negroes_. To the declaration in this case the defendant below, who is also the defendant in error, pleaded in abatement that the court could not take cognizance of the cause, because the plaintiff was not _a citizen_ of the State of Missouri, as averred in the declaration, but was a _negro of African descent_, and that his ancestors were of pure African blood, and were brought into this country and sold as _negro slaves_; and hence it followed, from the second section of the third article of the Constitution, which creates the judicial power of the United States, with respect to controversies between citizens of different States, that the Circuit Court could not take cognizance of the action.