Leyes Nuevas
The New Laws (Leyes Nuevas) were issued in 1542 by Emperor Charles V, largely thanks to the campaigning of Fray Bartolomé de las Casas, a Dominican friar who denounced the abuse of Indigenous people. They prohibited enslaving Indigenous people and sought to limit the encomienda system, under which colonists exploited Indigenous labor.
Colonists resisted the laws and they were only partially enforced, but they marked an important attempt by the Spanish Crown to protect the native population. Do not confuse them with the Reform Laws (Leyes de Reforma) of the 1850s, which dealt with separating church and state.