Scranton, Pa. ? Leaders of a Pennsylvania town that cracked down on illegal immigrants went to court to defend their practices Monday, as a judge in Missouri ruled that nearly identical ordinances in a St. Louis suburb violate state law.

The Valley Park, Mo., ordinances were taken almost verbatim from those of Hazleton, Pa., which fines landlords who rent to illegal immigrants and denies business permits to companies that employ them. Another measure requires tenants to register with City Hall.

Dozens of cities and towns across the country followed the lead of Hazleton, whose lawyers made opening statements Monday in a lawsuit filed by Hispanic groups and the American Civil Liberties Union. The plaintiffs argue that the city is unconstitutionally taking federal powers for itself.

“This is the day we’ve been waiting for a long time,” Mayor Lou Barletta said outside the federal courthouse in Scranton, north of Hazleton. “Small cities can no longer sit back and wait for the federal government to do something.”

In opening statements, an ACLU attorney told the judge there is no evidence to back up the Hazleton mayor’s claim that illegal immigrants are destroying the quality of life in his city.

“Even if illegal immigrants really are wreaking havoc on Hazleton, that doesn’t change the legal analysis” that the crackdown usurps the federal government’s role, said Witold “Vic” Walczak, the Pennsylvania legal director of the American Civil Liberties Union.

Kris Kobach, chairman of the Republican Party in Kansas and a law professor representing Hazleton in the case, said the town has welcomed immigrants throughout its history.

But after 2000, “something had changed. Hazleton had seen new criminals and new sorts of crime,” said Kobach, an immigration adviser under former Attorney General John Ashcroft.