Justices of the Supreme Court found a procedural flaw in the case involving ?neutrality agreements?, and therefore were unable to decide the case, although Justices Breyer, Sotomayor, and Kagan all dissented. The decision not to rule on the case means that the decision rendered by the 11th Circuit of Appeals court stands which means that the U.S. is split over whether neutrality agreements constitute ?a thing of value? and therefore may not be something exchanged in the union-employer relationship. The Justices in the Majority believed that because the contract had expired before the 11th circuit court had heard the case so its ruling may have been moot, also the employee who brought suit may have not been legally able to.
See "Supreme Court drops case on employer-union ?neutrality agreements?", Robert Barnes, The Washington Post, December 10, 2013