Senate Bill 4 has drawn its first lawsuit.

The League of United Latin American Citizens, Maverick County and the city of El Cenizo sued the state of Texas on Monday, claiming that SB 4 has failed to properly define a “sanctuary city,” and that the city and county — both on the border with Mexico — have kept their residents safe by choosing to operate as sanctuaries since 1999.

El Cenizo, in Webb County, has about 3,300 residents, many of whom are undocumented immigrants. The lawsuit claims that “Plaintiffs are safer when all people, including undocumented immigrants, feel safe when their local law enforcement officers can be trusted for reporting crimes or just speaking with them about issues in the community."

SB 4, which Gov. Greg Abbott signed into law on Sunday, allows peace officers to question the immigration status of people they legally detain or arrest, and it also allows for the punishment of department heads and elected officials who don’t cooperate with federal immigration agents. Abbott and other supporters of the bill insist it’s needed to enforce the rule of law and deter people who are already in the country illegally from committing more crimes.

El Cenizo and Maverick County's lawsuit, filed in a San Antonio federal court, argues that the new law violates both the Texas and U.S. constitutions.

The lawsuit comes on the heels of state Attorney General Ken Paxton’s preemptive lawsuit, filed Monday less than 24 hours after Abbott signed SB 4 into law. Paxton's lawsuit asks a federal court to declare the law constitutional.

El Cenizo and Maverick County say detaining people longer to allow U.S. Immigration and Customs Enforcement to decide whether to take them into federal custody — SB 4 requires local jurisdictions to honor federal detainer requests — ties up scarce law enforcement personnel and resources.