On closing the testimony in the court below, the counsel for the plaintiff prayed the court to instruct the jury, upon the agreed state of facts, that they ought to find for the plaintiff; when the court refused, and instructed them that, upon the facts, the law was with the defendant. With respect to the plea in abatement, which went to the citizenship of the plaintiff, and his competency to bring a suit in the Federal courts, the common-law rule of pleading is, that upon a judgment against the plea on demurrer, and that the defendant answer over, and the defendant submits to the judgment, and pleads over to the merits, the plea in abatement is deemed to be waived, and is not afterwards to be regarded as a part of the record in deciding upon the rights of the parties. There is some question, however, whether this rule of pleading applies to the peculiar system and jurisdiction of the Federal courts. As, in these courts, if the facts appearing on the record show that the Circuit Court had no jurisdiction, its judgment will be reversed in the appellate court for that cause, and the case remanded with directions to be dismissed. In the view we have taken of the case, it will not be necessary to pass upon this question, and we shall therefore proceed at once to an examination of the case upon its merits. The question upon the merits, in general terms, is, whether or not the removal of the plaintiff, who was a slave, with his master, from the State of Missouri to the State of Illinois, with a view to a temporary residence, and after such residence and return to the slave State, such residence in the free State works an emancipation. As appears from an agreed statement of facts, this question has been before the highest court of the State of Missouri, and a judgment rendered that this residence in the free State has no such effect; but, on the contrary, that his original condition continued unchanged. The court below, the Circuit Court of the United States for Missouri, in which this suit was afterwards brought, followed the decision of the State court, and rendered a like judgment against the plaintiff. The argument against these decisions is, that the laws of Illinois, forbidding slavery within her territory, had the effect to set the slave free while residing in that State, and to impress upon him the condition and status of a freeman; and that, by force of these laws, this status and condition accompanied him on his return to the slave State, and of consequence he could not be there held as a slave.