There were a few instances that a Pope would seemingly take a position which opposed the subduing, vanquishing, capturing and reducing persons to perpetual slavery. Such as Eugene in the mid 15th century who raised questions about enslaving converted Indigenous Peoples. But none issued a complete and formal Bull on the issue until Pope Paul III in June of 1537 when he wrote Sublimis Deus [sublime God]. This Papal Bull is considered by some to have rescinded all the previous Papal Bulls, edicts, letters and public statements that supported domination and slavery. Others feel it is a positive step but doesn’t really address all the elements necessary to reverse the negative results of colonization.
“We, who, though unworthy, exercise on earth the power of our Lord and seek with all our might to bring those sheep of His flock who are outside into the fold committed to our charge, consider, however, that the Indians are truly men and that they are not only capable of understanding the Catholic Faith but, according to our information, they desire exceedingly to receive it. Desiring to provide ample remedy for these evils, We define and declare by these Our letters, or by any translation thereof signed by any notary public and sealed with the seal of any ecclesiastical dignitary, to which the same credit shall be given as to the originals, that, notwithstanding whatever may have been or may be said to the contrary, the said Indians and all other people who may later be discovered by Christians, are by no means to be deprived of their liberty or the possession of their property, even though they be outside the faith of Jesus Christ; and that they may and should, freely and legitimately, enjoy their liberty and the possession of their property; nor should they be in any way enslaved; should the contrary happen, it shall be null and have no effect.”
This Papal Bull was fully rescinded about a year later in a June 1538 letter from Paul to King Charles V of Spain, Paul’s was responding to a letter in which Charles had pleaded on behalf of the conquistadors to reverse the Sublimes Deus Bull because it was ‘damaging’ the important tasks of colonization and for spreading the word of God.