FWIW, here is what the California Penal Code has to say about nitrous oxide:

381b. Any person who possesses nitrous oxide or any substance containing nitrous oxide, with the intent to breathe, inhale, or ingest for the purpose of causing a condition of intoxication, elation, euphoria, dizziness, stupefaction, or dulling of the senses or for the purpose of, in any manner, changing, distorting, or disturbing the audio, visual, or mental processes, or who knowingly and with the intent to do so is under the influence of nitrous oxide or any material containing nitrous oxide is guilty of a misdemeanor. This section shall not apply to any person who is under the influence of nitrous oxide or any material containing nitrous oxide pursuant to an administration for the purpose of medical, surgical, or dental care by a person duly licensed to administer such an agent.