You're assuming going to a movie is a "right" in the first place. It isn't. It is a privilege. A theatre, on the other hand, has an obligation to provide the best level of service to its patrons. If that means refusing service to a group of patrons because of legitimate concerns that they will become disruptive, then the theatre is well within its rights to do so. While a theatre cannot use this argument to discriminate on the basis of race, sex, or ethnicity, there is no statute that prevents the exclusion of minors. The whole purpose of the ratings system is so that the industry can police itself without the need for government interference. If the government is getting in the way of that, as was the case by the judge even allowing this to come to trial, the legislators need to know.