The enactment which established the restrictive geographical line was acquiesced in rather than approved by the States of the Union. It stood on the statute book, however, for a number of years; and the people of the respective States acquiesced in the reenactment of the principle as applied to the State of Texas, and it was proposed to acquiesce in its further application to the territory acquired by the United States from Mexico. But this proposition was successfully resisted by the representatives from the Northern States, who, regardless of the statute line, insisted upon applying restriction to the new territory generally, whether lying north or south of it, thereby repealing it as a legislative compromise, and, on the part of the North, persistently violating the compact, if compact there was.
Thereupon this enactment ceased to have binding virtue in any sense, whether as respects the North or the South, and so in effect it was treated on the occasion of the admission of the State of California and the organization of the Territories of New Mexico, Utah, and Washington.
Such was the state of this question when the time arrived for the organization of the Territories of Kansas and Nebraska. In the progress of constitutional inquiry and reflection it had now at length come to be seen clearly that Congress does not possess constitutional power to impose restrictions of this character upon any present or future State of the Union. In a long series of decisions, on the fullest argument and after the most deliberate consideration, the Supreme Court of the United States had finally determined this point in every form under which the question could arise, whether as affecting public or private rights—in questions of the public domain, of religion, of navigation, and of servitude.
The several States of the Union are by force of the Constitution coequal in domestic legislative power. Congress can not change a law of domestic relation in the State of Maine; no more can it in the State of Missouri. Any statute which proposes to do this is a mere nullity; it takes away no right, it confers none. If it remains on the statute book unrepealed, it remains there only as a monument of error and a beacon of warning to the legislator and the statesman. To repeal it will be only to remove imperfection from the statutes, without affecting, either in the sense of permission or of prohibition, the action of the States or of their citizens.
Still, when the nominal restriction of this nature, already a dead letter in law, was in terms repealed by the last Congress, in a clause of the act organizing the Territories of Kansas and Nebraska, that repeal was made the occasion of a widespread and dangerous agitation.