The Kentucky Supreme Court has upheld the state’s so-called “right-to-work” law, which makes it illegal to require workers to join unions and bars the collection of fees from private-sector workers who choose not to become union members. Rejecting a challenge by the Kentucky AFL-CIO and other unions, the court in a 4-3 decision on Thursday said the promotion of economic development and job growth formed the “rational basis” that the state needed to justify passing the law.