1, who decides? Anyway, Rav Ovadia says that there is (Yechavei Daat 4:65 and 5:64).
CTL,
a. Rav Moshe says that if he was sold in order to free him there is no problem. This is his solution to adopting a non-Jewish child who might do miun when he grows up IM, YD 1:162.
b. The 13th Amendment only says that slavery shall not exist and that Congress may enforce it by appropriate legislation. Is there a law that bars buying someone in order to free him? What if he was bought in a country that allows slavery?