Diversity in the service of freedom might be a very good thing. Diversity in the service of slavery might be a very bad thing. - Harry V. Jaffa

[I]t is impossible for men who exercise their reason to believe that any one part of the human race has been marked out by God or nature as so superior to any other. No man is by nature, or by manifest declaration of God's will, the possessor or possession, the master or slave, of another. Whoever asserts such a right to such domination or possession is, in Congress's words from that same document, 'rightfully resistible'.

The American Revolution and the Civil War were not merely discrete events. They constitute the first and last acts of a single drama. The fourscore and seven years between the Declaration of Independence and the Gettysburg Address comprehended the action of a tremendous world-historical tragedy.

Now the Constitution doesn’t say how this right is to be enforced, but it says it shall be done. And from 1793 to 1850 it depended upon the states honoring the Act. Well, that was not working, and so this federal law was substituted which provided enforcement procedures under the auspices of the federal government.