A politically conservative legal group filed a class-action suit against the Chicago Teachers Union over mandatory payments.The National Right to Work Legal Defense Foundation last week announced it filed a federal suit over a union policy limiting when teachers can opt out of paying fees.The suit, filed in the U.S. District Court for the Northern District, claims CTU violated the First Amendment by refusing to allow two teachers to discontinue paying fees when they requested to do so.The mandatory fees were deemed a free …