GROVES v. SLAUGHTER
Slaughter took a group of slaves to Mississippi to sell them. He accepted partial payment. The note fell due but remained unpaid. A federal court eventually held that Slaughter was entitled to recover the amount of the contract. However, a state constitutional provision adopted prior to Slaughter's sale prohibited his transaction.
Does the Mississippi constitutional provision banning importation and sale of slaves unconstitutionally encroach on congressional commerce power?
The provision did not become effective until a supporting statute was enacted, but that supporting statute followed the sale in question. Hence, the contract was valid.