A total of 11 motorbikes and one quad bike have been seized in Kings Forest, near Bury St Edmunds.
Suffolk police said on Twitter that those "abusing" the Icklingham Site of Special Scientific Interest are not welcome after the incident on Monday, March 29.
Fines were also given to those riding around the forest, with 19 penalty notices handed out for illegal Covid-19 behaviour and 10 for no insurance by the joint Suffolk and Bedfordshire teams.
Suffolk police added: "When ridden in public, [motorbikes] must have valid insurance. Most byways are actually classified as roads, so they need to be fully road legal.
"This is unacceptable behaviour and we’ll continue to target this as we really appreciate how this impacts on those that live and visit this lovely area.
"We’ll be back again soon, so don’t chance it."
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