For the summer when I was 16 I decided to work as a lifeguard since the pool was located close to my house and it was very convenient. I eventually got used to denying certain items such as tubes and balls, since they obstruct view and interfere with work, and for the most part this was understood with the patrons. We did have the ability to make rules.
I don't believe it was stated on the rules that food wasn't allowed, but our management did want us to reject it. One day though we allowed a group to bring in food since they had a large amount of home-made dishes and they planned to host a child's party under the gazebo, which seemed perfect for the occasion. We would have felt bad for all the work they put into this day and they even confirmed ahead of time that bringing food wasn't against the rules.
Following this though, more and more people began bringing food and mentioned the above incident when we tried to deny them. This lead to less sanitary conditions we couldn't handle while working and multiple bottles of alcohol being found. The integrity of the lifeguards was subsequently at stake too and it eventually lead to further disagreements between the guards and the rules.
How should we respond to patrons bringing food after the incident?