Attorneys for Iowa’s two largest public employee unions asked the state’s highest court Wednesday to strike down changes in collective bargaining laws they say unconstitutionally treat some union members differently than others in contract negotiations. In separate cases, thousands of members of the American Federation of State, County and Municipal Employees Council 61 and the Iowa State Education Association are asking the Iowa Supreme Court to consider whether the revised collective bargaining law passed and signed in February 2017 violates the Iowa Constitution.