Yancey's previous 1848 attempt at demanding a slave code for the territories was his Alabama Platform, which was in response to the Northern Wilmot Proviso attempt at banning slavery in territories conquered from Mexico. Justice Peter V. Daniel wrote a letter about the Proviso to former President Martin Van Buren: "It is that view of the case which pretends to an insulting exclusiveness or superiority on the one hand, and denounces a degrading inequality or inferiority on the other; which says in effect to the Southern man, 'Avaunt! you are not my equal, and hence are to be excluded as carrying a moral taint with you.' Here is at once the extinction of all fraternity, of all sympathy, of all endurance even; the creation of animosity fierce, implacable, undying." Both the Alabama Platform and the Wilmot Proviso failed, but Yancey learned to be less overtly radical in order to get more support. Southerners thought they were merely demanding equality, in that they wanted Southern property in slaves to get the same (or more) protection as Northern forms of property.