Hazleton, Pa. ? Advocates for immigrants sued the city of Hazleton on Monday, seeking to block an ordinance that would impose steep fines on landlords who rent to people living in the country illegally.

In its lawsuit filed in federal court in Scranton, the American Civil Liberties Union said the ordinance and a companion measure set to take effect Wednesday violate the Constitution because they trample on the federal government’s exclusive power to regulate immigration.

The laws would impose heavy fines on landlords who rent to illegal immigrants, deny business permits to companies that employ them, and require renters to register and purchase a renter’s permit at City Hall.

The plaintiffs – which also include the Puerto Rican Legal Defense and Education Fund, several illegal immigrants facing eviction, landlords, and a businessman – said they also would seek a federal injunction blocking the laws.