I’m sure you’re right. In any event, I’ve never seen anything official that this student’s actions were a violation of any kind of rule or law.
The Congressman -- who had long been in office and was not aging well -- then realized that he had been recorded and was in political peril because of his comments. So he tried to grab the student's recorder, and to make him give it up, began to choke him. As the kid squirmed and resisted, a teacher intervened and the issue was referred to the principal. Under threat, the student held firm and, on the advice of his father, insisted on a ruling by the local prosecutor.
Initially, a staff lawyer in the prosecutor's office made noises to the effect that the kid was in big trouble and should give the audio tape to the Congressman before an official inquiry was launched. Fortunately, the kid's parents lawyered up and the local paper -- a major daily -- learned of the incident. The elected prosecutor himself swiftly ruled that the kid had done nothing wrong because the recording had been made at a public event.
The Congressman and the school authorities of course had behaved badly and swiftly retreated into self protective versions and explanations of the episode. If something like it happened today, the kid would be on Fox News the next day and the Congressman and the school would be sweating out bad publicity and the risk of a lawsuit.