The Missouri Compromise of 1820 admitted Maine as a "free" state and Missouri as a "slave" state. As part of the deal, slavery will be, from then on, prohibited north of parallel 36°30', with the exception of the state of Missouri which was located north of that parallel.
Section 14 of the Constitution states that all citizens of the United States are subject to the jurisdiction of the country. Therefore, no other state may enforce a law that may limit the privileges provided by the being a citizen of the country. The compromise is clearly making a difference between the privileges of citizens of the country according to the place they live.
Section 32 of the Constitution states that no person is entitled to a different set of emoluments (or payments he receives for the work he or she does) than those from the community he lives. The Missouri compromise also goes against this enactment due to the fact that slaves are clearly getting separate forms of payment.