I would recommend a gradual escalation of the problem. First making it non specific then getting more pointed.
One way to approach it would:
1. request the EC send out a letter to all residents reminding them of their obligations in this regard.
2. If it persists ask the EC to send a letter specifically to the offending neighbours.
3. If it persists after that there has to be a formal complaint made (by either you or the EC) and then a notice to comply issued.