The courts of Louisiana having held, for a series of years, that where a master took his slave to France, or any free State, he was entitled to freedom, and that on bringing him back the status of slavery did not attach, the Legislature of Louisiana declared by an act that the slave should not be made free under such circumstances. This regulated the rights of the master from the time the act took effect. But the decision of the Missouri court, reversing a former decision, affects all previous decisions, technically, made on the same principles, unless such decisions are protected by the lapse of time or the statute of limitations. Dred Scott and his family, beyond all controversy, were free under the decisions made for twenty-eight years, before the case of Scott _v._ Emerson. This was the undoubted law of Missouri for fourteen years after Scott and his family were brought back to that State. And the grave question arises, whether this law may be so disregarded as to enslave free persons. I am strongly inclined to think that a rule of decision so well settled as not to be questioned, cannot be annulled by a single decision of the court. Such rights may be inoperative under the decision in future; but I cannot well perceive how it can have the same effect in prior cases. It is admitted, that when a former decision is reversed, the technical effect of the judgment is to make all previous adjudications on the same question erroneous. But the case before us was not that the law had been erroneously construed, but that, under the circumstances which then existed, that law would not be recognised; and the reason for this is declared to be the excitement against the institution of slavery in the free States. While I lament this excitement as much as any one, I cannot assent that it shall be made a basis of judicial action. In 1816, the common law, by statute, was made a part of the law of Missouri; and that includes the great principles of international law. These principles cannot be abrogated by judicial decisions. It will require the same exercise of power to abolish the common law, as to introduce it. International law is founded in the opinions generally received and acted on by civilized nations, and enforced by moral sanctions. It becomes a more authoritative system when it results from special compacts, founded on modified rules, adapted to the exigencies of human society; it is in fact an international morality, adapted to the best interests of nations. And in regard to the States of this Union, on the subject of slavery, it is eminently fitted for a rule of action, subject to the Federal Constitution. "The laws of nations are but the natural rights of man applied to nations." (Vattel.)