His family, of French origin, originally named Casaus, settled in Seville. His father accompanied Columbus on his second voyage and brought Bartolome as Taino slave as a trophy. which at that point in his life did not concern him.
Bartolome obtained a law degree and sailed to the Indies on the third voyage of Columbus 1n 1498, acquiring slaves and land under the encomienda system. But by 1510 he had become a secular priest, without yet giving up his possessions. He did however oppose the Spanish treatment of the Indian slaves, who were harshly treated and forced to labor hard at tasks for which they had not training. By 1514 however, as his conversion depended, he renounced all claim on his Indian serfs.
He made a series of voyages to Spain to gain support for towns were the Spainish and Indians could live together in equality. They dying King Ferdinand gave him the title of "Protector of the Indians" and a set of laws which were largely ignored, in spite of Barthome's efforts. The Dominicans had preached against slavery and Bartholome followed suit with his own sermons. By 1523 he joined the Dominicans.
He began to write on the history of the Indies. He was made the Domican Vicar of Guatamala and helped draw up petitions to the Pope on behalf of the Indians. He persuaded the Spanish not to use force in Guatemala and used peaceful means of conversion. He remained it Vera Paz. He founded what today is the oldest church in Central America, at Rabinal, Guatemala where my friend Tim Conlan is (see http://roominhouseblues.blogspot.com/2010/12/these-blog-is-about-all-those-who.html)
He made several trips to Spain to defend himself from charges, debate his opponents publically, and petition the court for support of his policies. In 1542 he got the "New Laws" that abolished slavery and the encomienda system.
But his opponents maneuvered to get him appointed a Bishop hoping that his hands would be tied to a Bishopric and he would not be free to travel to Spain or elsewhere in Latin America. He accepted the Bishopric of impoverished Chiapas hoping to settle up model communities there. He went to Chiapas with 45 Dominican missionaries. His efforts in Chiapas nearly cost him his life and he had soon to return to Spain to defend himself against the charge of high treason. He appointed vicars to enforce his run that no one who continued to profit off slavery could be granted absolution. He successfully debated his opponents and ultimately no verdict was handed down in the case.
He retired to a convent in Madrid where he published many works and fought King Phillip II plan to use Indian labor for mining gold in Peru. He remained largely in silence until his death.
The process of his beatification at Rome began in 2000, although he is already a saint on the Anglican calendar. Las Casas Institute at Blackfriars Hall, Oxford, was inspired by his work.
Similar to de las Casas was Bartolomeo de Olmedo, Chaplin to Cortez who tried to moderate his actions in Mexico. The two together are held up as examples of correct treatment of the indians.
Let your continual mercy, O Lord, enkindle in your Church the never-failing gift of charity, that, following the example of your servants Bartolome de Las Casas and Bartolomeo de Olmedo, we may have grace to defend the children of the poor, and maintain the cause of those who have no helper; for the sake of him who gave his life for us, your Son our Savior Jesus Christ, who lives and reigns with you and the Holy Spirit, one God, now and for ever.