The Free-Soil Party would have supported the Wilmot Proviso. This 1846 proposal aimed to ban slavery in any territory acquired from Mexico as a result of the Mexican-American War. The party was founded on the principles of opposing the expansion of slavery into the western territories, appealing to those who wanted to ensure that these lands were available for free settlers rather than slaveholders.
In contrast, the Free-Soil Party would not have supported the Fugitive Slave Act or slave codes, as these laws sought to enforce and maintain the institution of slavery, which the Free-Soil Party opposed.