The mere toleration of the slave trade could not make slavery itself - the right of property in man - lawful any where; not even on board the slave ship. Toleration of a wrong is not law.

It is perfectly clear, in the first place, that the constitution of the United States did not, of itself, create or establish slavery as a new institution; or even give any authority to the state governments to establish it as a new institution. The greatest sticklers for slavery do not claim this.

Slavery, if it can be legalized at all, can be legalized only by positive legislation. Natural law gives it no aid. Custom imparts to it no legal sanction.

Lysander Spooner Quotes