Guernsey Police are urging people to report beach parties while they are happening.
The force said they were only able to investigate parties while they were being held and not afterwards.
It follows complaints about an illegal party at Rousse on 4 June after which broken glass was left on the beach.
A hand-carved child's bench and garden gate, which were stolen from property on Les Picquerel Estate that night, were found in the remains of a bonfire.
Anyone planning a beach party has been reminded to seek permission from the Environment Department.
The Police should also be informed about any planned beach bonfires.