I believe the correct answer is the Constitution of the Republic of Texas 1836.
Explanation:
Before the Constitution of the Republic of Texas was ratified in 1836, history has it that, Texas was under the governance of Mexico with numerous constitutions, one of which was the Mexican Constitution of 1824. After Mexico came to Texas, slavery grew to the highest amount. However, Mexico refused to settle in Texas but encouraged the Anglo-Americans to settle in Texas. These countries saw the abundance Texas had to offer which made them decide to settle. As time went on, slavery caused a rift between the Mexican government and the settlers which resulted in the Texas revolution. After the revolution, Texas gained its independence and due to how much slavery had spread, the Constitution of 1836 legalised slavery. The Constitution of the Republic of Texas marked the independence of Texas. Section 9 of the Constitution specifically made slavery legal. It prohibited Congress from passing new laws against slave trade or any laws purported to release slaves.
