Owners of an Irish movie theater have been informed that they are breaking national communications law by employing a signal blocker to disable their patrons’ cell phones during screenings. The theater had installed the blocker as a response to an epidemic of moviegoers sending and receiving text messages on their phones, or even talking on them, while a film was playing. But as it turns out, such devices are illegal even to possess, and the use of one to block wireless transmissions carries a hefty fine.