Ravers planning to party the night away on Loe Bar beach near Helston have cancelled after police got wind of the event.
Officers contacted the organisers of the rave, which was being planned over Facebook to take place over the coming days, after a member of the public brought it to their attention.
A police spokesperson said: "Were the event to go ahead it would be trespassing on National Trust property and due to the number planning to attend and that music will be played it falls under legislation that would mean be classified as an illegal rave.
"We have spoken to the organiser of the event and they have posted a message on the original group page cancelling the event; asking for people not to attend."
The organisers were warned that if a rave did go ahead they could have their sound equipment could seized and be prosecuted, with a maximum sentence of three months in prison.
The spokesperson added: "We are not in the business of spoiling people’s fun but any event needs to be planned, organised and run in accordance with legislation so that those attending are safe to do so, any potential for criminality can be addressed and so that the impact on the local community is properly considered."
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