texas senate bill 4 was enacted in 2017 to block municipalities in texas form becoming sanctuary cities, that is, to prevent local authorities from refusing to cooperate with federal authorities in enforcing immigration laws by directing police and court officials not to question persons accused of crimes about their immigration status and to ignore requests by federal authorities to hold individuals who are in the country illegally and have been arrested for minor crimes for deportation. texas senate bill 4 also allows police officers to check the immigration status of those they detain if they choose.