The mayor of Hazleton, Pa., signed a city ordinance Friday that punishes people who do business with illegal immigrants or provide them with jobs or housing while critics called the new law unenforceable and predicted it will be overturned.

Mayor Lou Barletta said his office will soon begin to train city workers in how to check people’s immigration or citizenship status. He also expects the City Council to approve companion legislation requiring all tenants to register with the city and prove their legal residency.