The Sweet 16 of BSA Safety describe the measures we should use at all Scouting activities. The sixteenth point of the Sweet 16 is Discipline (see below).
Scouts can be instructed in the rules and understand them and still not follow them. Why does this happen? It is not necessarily because the Scouts are trying to be disrespectful. In many cases they are caught up in the fun of the moment. But if they are not following the instructions of the activity supervisor and it has the potential to become unsafe, it is time to step in.
Usually an explanation to the Scout of why they must listen and follow the directions is enough. When they understand we are just trying to keep them safe, they are cooperative. If this isn’t effective though, it might be time for more drastic measures, such as a call to the parents.
The more difficult situation is when the person who is not following the directions is an adult. It does happen from time to time. Although the point below only mentions youth, if you have an adult who has decided they don’t need to follow the safety instructions, then the youth might want to follow his lead. “Mr. Jones isn’t wearing his PFD, so why do I have to?” In this case it is usually helpful to enlist the assistance of a couple of other adults who will back you up and approach the adult as a group and ask them to comply.
From the Sweet 16 of BSA Safety on the Scouting.org website:
No supervisor is effective if he or she cannot control the activity and the individual participants. Youth must respect their leader and follow his or her direction.