Content rules engines for playback devices are disclosed herein. A media playback system receives a first command to form a synchrony group comprising a plurality of playback devices. The system receives a second command for the synchrony group to play back first audio content. In response to the second command, the first audio content is played back via the synchrony group. The system receives (i) second audio content to be played back by one or more of the playback devices of the synchrony group and (ii) content source properties associated with an audio source of the second audio content. The system accesses a rules engine to determine playback restrictions based at least in part on the content source properties. Based at least in part on the playback restrictions, operation of one or more of the playback devices is restricted.