A federal appeals court says changes to Michigan’s sex offender registry rules cannot be applied retroactively to thousands of sex offenders. In a 3-0 decision Thursday, a panel of the 6th U.S. Circuit Court of Appeals ruled that it’s unconstitutional to impose new restrictions on people convicted before the state’s registry law was updated in 2006 and in 2011. Michigan began prohibiting registrants from living, working or loitering within 1,000 feet of a school in 2006. Five years later, lawmakers added requirements that offenders be divided into three tiers based on the seriousness of their crimes. U.S. District Court Judge Robert Cleland ruled last year that those changes could be imposed retroactively. He ruled other portions of the law unconstitutional, but the 6th Circuit didn’t rule on those provisions.