To this I answer, that, in common with all the other legislative powers of Congress, it finds limits in the express prohibitions on Congress not to do certain things; that, in the exercise of the legislative power, Congress cannot pass an ex post facto law or bill of attainder; and so in respect to each of the other prohibitions contained in the Constitution.
Besides this, the rules and regulations must be needful. But undoubtedly the question whether a particular rule or regulation be needful, must be finally determined by Congress itself. Whether a law be needful, is a legislative or political, not a judicial, question. Whatever Congress deems needful is so, under the grant of power.
Nor am I aware that it has ever been questioned that laws providing for the temporary government of the settlers on the public lands are needful, not only to prepare them for admission to the Union as States, but even to enable the United States to dispose of the lands.
Without government and social order, there can be no property; for without law, its ownership, its use, and the power of disposing of it, cease to exist, in the sense in which those words are used and understood in all civilized States.
Since, then, this power was manifestly conferred to enable the United States to dispose of its public lands to settlers, and to admit them into the Union as States, when in the judgment of Congress they should be fitted therefor, since these were the needs provided for, since it is confessed that Government is indispensable to provide for those needs, and the power is, to make all needful rules and regulations respecting the territory, I cannot doubt that this is a power to govern the inhabitants of the territory, by such laws as Congress deems needful, until they obtain admission as States.
Whether they should be thus governed solely by laws enacted by Congress, or partly by laws enacted by legislative power conferred by Congress, is one of those questions which depend on the judgment of Congress—a question which of these is needful.
But it is insisted, that whatever other powers Congress may have respecting the territory of the United States, the subject of negro slavery forms an exception.
The Constitution declares that Congress shall have power to make "all needful rules and regulations" respecting the territory belonging to the United States.
The assertion is, though the Constitution says all, it does not mean all—though it says all, without qualification, it means all except such as allow or prohibit slavery. It cannot be doubted that it is incumbent on those who would thus introduce an exception not found in the language of the instrument, to exhibit some solid and satisfactory reason, drawn from the subject-matter or the purposes and objects of the clause, the context, or from other provisions of the Constitution, showing that the words employed in this clause are not to be understood according to their clear, plain, and natural signification.
The subject-matter is the territory of the United States out of the limits of every State, and consequently under the exclusive power of the people of the United States. Their will respecting it, manifested in the Constitution, can be subject to no restriction. The purposes and objects of the clause were the enactment of laws concerning the disposal of the public lands, and the temporary government of the settlers thereon until new States should be formed. It will not be questioned that, when the Constitution of the United States was framed and adopted, the allowance and the prohibition of negro slavery were recognised subjects of municipal legislation; every State had in some measure acted thereon; and the only legislative act concerning the territory—the ordinance of 1787, which had then so recently been passed—contained a prohibition of slavery. The purpose and object of the clause being to enable Congress to provide a body of municipal law for the government of the settlers, the allowance or the prohibition of slavery comes within the known and recognised scope of that purpose and object.