Now observe that this article, proviso and all, is part of an unalterable compact to which the Constitution has given validity. Nobody pretends Congress has ever had the power to alter it. Mr. TOOMBS denies any such power in express terms. A law which Congress cannot alter has substantially the force and effect of a constitutional proviso. This, then, is the only law for the reclamation of fugitive slaves in the five States of the northwest territory; and there can be no other, the Constitution having made it perpetually valid. Such obviously is the meaning and legal effect of the fugitive slave provision in the ordinance. And the meaning of that, derived as it is not merely from the consent of the Federal and State conventions, but from their concurrent action, necessarily fixes the meaning of the provision on the same subject in the Constitution, and shows how it must have been understood. As the two were parts of the same compromise, of course neither was understood to be inconsistent with the other. The provision in the Constitution is in these words: "No person held to service or labor in one State, under the laws thereof, escaping into another, shall, in consequence of any law or regulation therein, be discharged from such service or labor, but shall be delivered up on claim of the party to whom such service or labor may be due." So far as this describes, or was understood to describe, persons held to service or labor as slaves, it necessarily must also have been understood to apply only to the original States. This follows from what has already been shown. And it must have been so understood for another reason, because it was only "in" and "under" the laws of those States that persons could be held to service or labor as slaves. Under the laws of the Territories and new States, their being so held was forever prohibited. Hence, none but those escaped from one of the original States could ever be legally liable to reclamation, according to the understanding and intention of the original parties to this compact. This manifestly was the meaning of "the fathers," when the ordinance and Constitution were framed and ratified. The two provisions must be construed together. That in the ordinance was intended for the Territories and new States, and that in the Constitution for the original States. If that in the Constitution had been intended for the Territories, it would have read, "escaping into another State or into the Territory," and that in the ordinance would have been entirely omitted. The proviso to the prohibition in the Missouri Compromise in 1820 is a striking confirmation of this. That was copied, word for word, from the ordinance of 1787, or original compromise, except substituting for the words "in any one of the States," the words "in any State or Territory of the United States," as follows: