47 CFR § 97.101 - General standards.
(b) Each station licensee and each control operator must cooperate in selecting transmitting channels and in making the most effective use of the amateur service frequencies. No frequency will be assigned for the exclusive use of any station.
(c) At all times and on all frequencies, each control operator must give priority to stations providing emergency communications, except to stations transmitting communications for training drills and tests in RACES.
(d) No amateur operator shall willfully or maliciously interfere with or cause interference to any radio communication or signal.