Without going minutely into the details of each case, I will now give reference to two classes of acts, in one of which Congress has extended the ordinance of 1787, including the article prohibiting slavery, over different Territories, and thus exerted its power to prohibit it; in the other, Congress has erected Governments over Territories acquired from France and Spain, in which slavery already existed, but refused to apply to them that part of the Government under the ordinance which excluded slavery.

Of the first class are the act of May 7th, 1800, (2 Stat. at Large, 58,) for the government of the Indiana Territory; the act of January 11th, 1805, (2 Stat. at Large, 309,) for the government of Michigan Territory; the act of May 3d, 1809, (2 Stat. at Large, 514,) for the government of the Illinois Territory; the act of April 20th, 1836, (5 Stat. at Large, 10,) for the government of the Territory of Wisconsin; the act of June 12th, 1838, for the government of the Territory of Iowa; the act of August 14th, 1848, for the government of the Territory of Oregon. To these instances should be added the act of March 6th, 1820, (3 Stat. at Large, 548,) prohibiting slavery in the territory acquired from France, being northwest of Missouri, and north of thirty-six degrees thirty minutes north latitude.

Of the second class, in which Congress refused to interfere with slavery already existing under the municipal law of France or Spain, and established Governments by which slavery was recognised and allowed, are: the act of March 26th, 1804, (2 Stat. at Large, 283,) for the government of Louisiana; the act of March 2d, 1805, (2 Stat. at Large, 322,) for the government of the Territory of Orleans; the act of June 4th, 1812, (2 Stat. at Large, 743,) for the government of the Missouri Territory; the act of March 30th, 1822, (3 Stat. at Large, 654,) for the government of the Territory of Florida. Here are eight distinct instances, beginning with the first Congress, and coming down to the year 1848, in which Congress has excluded slavery from the territory of the United States; and six distinct instances in which Congress organized Governments of Territories by which slavery was recognised and continued, beginning also with the first Congress, and coming down to the year 1822. These acts were severally signed by seven Presidents of the United States, beginning with General Washington, and coming regularly down as far as Mr. John Quincy Adams, thus including all who were in public life when the Constitution was adopted.

If the practical construction of the Constitution contemporaneously with its going into effect, by men intimately acquainted with its history from their personal participation in framing and adopting it, and continued by them through a long series of acts of the gravest importance, be entitled to weight in the judicial mind on a question of construction, it would seem to be difficult to resist the force of the acts above adverted to.

It appears, however, from what has taken place at the bar, that notwithstanding the language of the Constitution, and the long line of legislative and executive precedents under it, three different and opposite views are taken of the power of Congress respecting slavery in the Territories.

One is, that though Congress can make a regulation prohibiting slavery in a Territory, they cannot make a regulation allowing it; another is, that it can neither be established nor prohibited by Congress, but that the people of a Territory, when organized by Congress, can establish or prohibit slavery; while the third is, that the Constitution itself secures to every citizen who holds slaves, under the laws of any State, the indefeasible right to carry them into any Territory, and there hold them as property.

No particular clause of the Constitution has been referred to at the bar in support of either of these views. The first seems to be rested upon general considerations concerning the social and moral evils of slavery, its relations to republican Governments, its inconsistency with the Declaration of Independence and with natural right.

The second is drawn from considerations equally general, concerning the right of self-government, and the nature of the political institutions which have been established by the people of the United States.

While the third is said to rest upon the equal right of all citizens to go with their property upon the public domain, and the inequality of a regulation which would admit the property of some and exclude the property of other citizens; and, inasmuch as slaves are chiefly held by citizens of those particular States where slavery is established, it is insisted that a regulation excluding slavery from a Territory operates, practically, to make an unjust discrimination between citizens of different States, in respect to their use and enjoyment of the territory of the United States.

With the weight of either of these considerations, when presented to Congress to influence its action, this court has no concern. One or the other may be justly entitled to guide or control the legislative judgment upon what is a needful regulation. The question here is, whether they are sufficient to authorize this court to insert into this clause of the Constitution an exception of the exclusion or allowance of slavery, not found therein, nor in any other part of that instrument. To engraft on any instrument a substantive exception not found in it, must be admitted to be a matter attended with great difficulty. And the difficulty increases with the importance of the instrument, and the magnitude and complexity of the interests involved in its construction. To allow this to be done with the Constitution, upon reasons purely political, renders its judicial interpretation impossible—because judicial tribunals, as such, cannot decide upon political considerations. Political reasons have not the requisite certainty to afford rules of juridical interpretation. They are different in different men. They are different in the same men at different times. And when a strict interpretation of the Constitution, according to the fixed rules which govern the interpretation of laws, is abandoned, and the theoretical opinions of individuals are allowed to control its meaning, we have no longer a Constitution; we are under the government of individual men, who for the time being have power to declare what the Constitution is, according to their own views of what it ought to mean. When such a method of interpretation of the Constitution obtains, in place of a republican Government, with limited and defined powers, we have a Government which is merely an exponent of the will of Congress; or what, in my opinion, would not be preferable, an exponent of the individual political opinions of the members of this court.