A U.S. judge on Thursday struck down as unconstitutional a local law designed to crack down on illegal immigration, dealing a blow to similar laws passed by dozens of towns and cities across the country.

U.S. District Judge James Munley said the city of Hazleton, 100 miles north of Philadelphia, was barred from implementing a law that would penalize businesses that hire illegal immigrants and fine landlords who rent rooms to them.

The law also sought to establish English as the Pennsylvania town's official language.

Federal law prohibits Hazleton from enforcing any of the provisions of its ordinances, Munley wrote in a 206-page opinion following a federal trial in which civil rights groups challenged Hazleton's law.

The city of 30,000 blames a recent rise in illegal immigration for boosting crime and overburdening social services. The law was passed in July 2006 but not applied because opponents won a court injunction.

About a third of the city's residents are immigrants from Central America and around a quarter of the immigrant population is believed to be undocumented, civil rights campaigners say.

Groups including the American Civil Liberties Union successfully argued that local authorities such as Hazleton have no right to regulate immigration, which is the sole responsibility of the federal government.

Whatever frustrations the City of Hazleton may feel about the current state of federal immigration enforcement, the nature of the political system of the United States prohibit the city from enacting ordinances that disrupt a carefully drawn federal statutory scheme, Munley wrote.

'RIPE FOR APPEAL'

The judge added that the U.S. Constitution protects all its residents. The genius of our Constitution is that it provides rights even to those who evoke the least sympathy from the general public.

Hazleton Mayor Lou Barletta said the city would take the case to the 3rd U.S. Circuit Court of Appeals in Philadelphia, and to the U.S. Supreme Court if necessary.

Hazleton isn't going to back down, Barletta, a Republican who has become a national voice for the local fight against illegal immigration, told a news conference on the steps of Hazleton City Hall.

I will do everything I can to make Hazleton the toughest city in America for illegal immigrants, he said. I will not sit back because the federal government has refused to do its job.

Hazleton attorney Kris Kobach called the judge's decision a paradigm of judicial activism and said the case was ripe for appeal.

Immigrants rights campaigners say about 100 towns and cities have modeled their immigration laws on Hazleton in a bid to deal with an estimated 12 million illegal immigrants living in the United States.

But none has been implemented because authorities are awaiting the outcome of the Hazleton case, the first to be subjected to a full trial in federal court, said Vic Walczak, legal director for the ACLU in Pennsylvania.

Similar measures have recently been withdrawn or modified in Valley Park, Missouri, and Escondido, California, said Omar Jadwat, an attorney with the ACLU.

This (decision) deals a body blow to efforts by localities to try to regulate immigration, said Foster Maer, an attorney with the Puerto Rican Legal Defense and Education Fund.

Immigration Pennsylvania