French consumer association Union Federale des Consommateurs-Que Choisir has sued Apple and Sony over their proprietary music formats, claiming that their digital rights management ("DRM") harms consumers. Both Apple and Sony use DRM systems which prevents music purchased online from their music stores from being played on competitors' media players. The consumer group claims that the "total absence of interoperability" not only harms consumer rights, but "also constitutes a significant restraint on the free circulation of creative works." The lawsuits follow an action launched earlier this year against Apple by a disgruntled American consumer, who claimed Apple's proprietary DRM format violates US antitrust laws.