It would not be easy for the Legislature to employ more explicit language to signify its will that the status of slavery should not exist within the Territory, than the words found in the act of 1820, and in the ordinance of 1787; and if any doubt could exist concerning their application to cases of masters coming into the Territory with their slaves to reside, that doubt must yield to the inference required by the words of exception. That exception is, of cases of fugitive slaves. An exception from a prohibition marks the extent of the prohibition; for it would be absurd, as well as useless, to except from a prohibition a case not contained within it. (9 Wheat., 200.) I must conclude, therefore, that it was the will of Congress that the state of involuntary servitude of a slave, coming into the Territory with his master, should cease to exist. The Supreme Court of Missouri so held in Rachel v. Walker, (4 Misso. R., 350,) which was the case of a military officer going into the Territory with two slaves.
But it is a distinct question, whether the law of Missouri recognised and allowed effect to the change wrought in the status of the plaintiff, by force of the laws of the Territory of Wisconsin.
I say the law of Missouri, because a judicial tribunal, in one State or nation, can recognise personal rights acquired by force of the law of any other State or nation, only so far as it is the law of the former State that those rights should be recognised. But, in the absence of positive law to the contrary, the will of every civilized State must be presumed to be to allow such effect to foreign laws as is in accordance with the settled rules of international law. And legal tribunals are bound to act on this presumption. It may be assumed that the motive of the State in allowing such operation to foreign laws is what has been termed comity. But, as has justly been said, (per Chief Justice Taney, 13 Pet., 589,) it is the comity of the State, not of the court. The judges have nothing to do with the motive of the State. Their duty is simply to ascertain and give effect to its will. And when it is found by them that its will to depart from a rule of international law has not been manifested by the State, they are bound to assume that its will is to give effect to it. Undoubtedly, every sovereign State may refuse to recognise a change, wrought by the law of a foreign State, on the status of a person, while within such foreign State, even in cases where the rules of international law require that recognition. Its will to refuse such recognition may be manifested by what we term statute law, or by the customary law of the State. It is within the province of its judicial tribunals to inquire and adjudge whether it appears, from the statute or customary law of the State, to be the will of the State to refuse to recognise such changes of status by force of foreign law, as the rules of the law of nations require to be recognised. But, in my opinion, it is not within the province of any judicial tribunal to refuse such recognition from any political considerations, or any view it may take of the exterior political relations between the State and one or more foreign States, or any impressions it may have that a change of foreign opinion and action on the subject of slavery may afford a reason why the State should change its own action. To understand and give just effect to such considerations, and to change the action of the State in consequence of them, are functions of diplomatists and legislators, not of judges.
The inquiry to be made on this part of the case is, therefore, whether the State of Missouri has, by its statute, or its customary law, manifested its will to displace any rule of international law, applicable to a change of the status of a slave, by foreign law.
I have not heard it suggested that there was any statute of the State of Missouri bearing on this question. The customary law of Missouri is the common law, introduced by statute in 1816. (1 Ter. Laws, 436.) And the common law, as Blackstone says, (4 Com., 67,) adopts, in its full extent, the law of nations, and holds it to be a part of the law of the land.
I know of no sufficient warrant for declaring that any rule of international law, concerning the recognition, in that State, of a change of status, wrought by an extra-territorial law, has been displaced or varied by the will of the State of Missouri.
I proceed then to inquire what the rules of international law prescribe concerning the change of status of the plaintiff wrought by the law of the Territory of Wisconsin.
It is generally agreed by writers upon international law, and the rule has been judicially applied in a great number of cases that wherever any question may arise concerning the status of a person, it must be determined according to that law which has next previously rightfully operated on and fixed that status. And, further, that the laws of a country do not rightfully operate upon and fix the status of persons who are within its limits in itinere, or who are abiding there for definite temporary purposes, as for health, curiosity, or occasional business; that these laws, known to writers on public and private international law as personal statutes, operate only on the inhabitants of the country. Not that it is or can be denied that each independent nation may, if it thinks fit, apply them to all persons within their limits. But when this is done, not in conformity with the principles of international law, other States are not understood to be willing to recognise or allow effect to such applications of personal statutes.
It becomes necessary, therefore, to inquire whether the operation of the laws of the Territory of Wisconsin upon the status of the plaintiff was or was not such an operation as these principles of international law require other States to recognise and allow effect to.
And this renders it needful to attend to the particular facts and circumstances of this case.