US District Judge Robert Pratt issued an order blocking enforcement of an Iowa law that prohibits sex offenders from living within 2,000 feet of a school or day care center.  The order came in a federal lawsuit filed by the Iowa Civil Liberties Union last month and expanded Friday to include all people who are subject to the residency restriction.  The lawsuit said the requirement makes it nearly impossible for an offender to find a place to live because there is virtually no place in towns or urban areas in Iowa that is not within 2,000 feet of a school or daycare center.  Authorities have said since the law took effect, they have seen halfway houses fill up with sex offenders who have no place to go.