It further increased tensions between the North and the South, Ban slavery in land obtained from Mexico, Southerners opposed the Wilmot Proviso. This is because the Wilmot Proviso, established peace with Mexico, and the land that Mexico owned was in the South, To keep slavery out of any lands obtained from Mexico, The Wilmot Proviso was an 1846 proposal that outlawed slavery in any territory, gained from the War with Mexico, Introduced by David Wilmont, the Wilmot proviso proposed to ban slavery in any, territory gained from, or after the Mexican-American War, etc...