2. If it had jurisdiction, is the judgment it has given erroneous or not?

The plaintiff in error, who was also the plaintiff in the court below, was, with his wife and children, held as slaves by the defendant, in the State of Missouri; and he brought this action in the Circuit Court of the United States for that district, to assert the title of himself and his family to freedom.

The declaration is in the form usually adopted in that State to try questions of this description, and contains the averment necessary to give the court jurisdiction; that he and the defendant are citizens of different States; that is, that he is a citizen of Missouri, and the defendant a citizen of New York.

The defendant pleaded in abatement to the jurisdiction of the court, that the plaintiff was not a citizen of the State of Missouri, as alleged in his declaration, being a negro of African descent, whose ancestors were of pure African blood, and who were brought into this country and sold as slaves.

To this plea the plaintiff demurred, and the defendant joined in demurrer. The court overruled the plea, and gave judgment that the defendant should answer over. And he therefore put in sundry pleas in bar, upon which issues were joined; and at the trial the verdict and judgment were in his favor. Whereupon the plaintiff brought this writ of error.

Before we speak of the pleas in bar, it will be proper to dispose of the questions which have arisen on the plea in abatement.

That plea denies the right of the plaintiff to sue in a court of the United States, for the reasons therein stated.

If the question raised by it is legally before us, and the court should be of opinion that the facts stated in it disqualify the plaintiff from becoming a citizen, in the sense in which that word is used in the Constitution of the United States, then the judgment of the Circuit Court is erroneous and must be reversed.

It is suggested, however, that this plea is not before us; and that as the judgment in the court below on this plea was in favor of the plaintiff, he does not seek to reverse it, or bring it before the court for revision by his writ of error; and also that the defendant waived this defense by pleading over, and thereby admitted the jurisdiction of the court.

But in making this objection, we think the peculiar and limited jurisdiction of courts of the United States has not been adverted to. This peculiar and limited jurisdiction, has made it necessary, in these courts, to adopt different rules and principles of pleading, so far as jurisdiction is concerned, from those which regulate courts of common law in England, and in the different States of the Union which have adopted the common-law rules.