A federal judge has barred Albuquerque from enforcing an ordinance that banned sex offenders from using public libraries, saying the law, as written, violated First Amendment rights.

U.S. District Judge M. Christina Armijo says she struggled to strike a proper legal balance in the case, since city officials have a legitimate interest in protecting children from harm, danger and crime, "especially crimes of a sexual nature."

On the other hand, the judge said in a 42-page opinion that sex offenders, "no matter how reviled," have constitutional rights.

The case was filed in 2008 by the American Civil Liberties Union of New Mexico on behalf of a John Doe plaintiff.