Final answer:
La Casa stopped being a bishop in 1582 due to his advocacy for indigenous rights. His resignation in 1566 marked the end of his tenure as a bishop.
Step-by-step explanation:
La Casa stopped being a bishop in 1582. This happened because La Casa, whose full name was Bartolomé de Las Casas, was a Dominican friar and was deeply involved in advocating for the rights of the indigenous peoples in the Spanish colonies. He wrote extensively on the mistreatment and abuse of the indigenous population, which put him at odds with the Spanish authorities. In 1550, he presented his arguments at the Valladolid debate, a public debate held in Spain, where he argued against the encomienda system and defended the humanity of the indigenous people. While he continued to fight for indigenous rights after the debate, his influence waned over time, and he eventually resigned from his position as bishop in 1566. He passed away in 1566.