Police in Northumberland stopped 45 motorcyclists taking part in Sunday’s EU demonstration and issued them with warnings for allegedly riding in an anti-social manner.
If they are deemed to be riding anti-socially again within the next 12 months, their bikes can be seized under the Police Reform Act.
Chief Supt Gordon Milward said: "While the majority of bikers protested in a responsible manner, a minority were intent on causing traffic disruption. As a result, 45 bikers were stopped and issued with Section 59 Police Reform Act warnings."
The riders were among 700 on an A1 ride from Washington Services, footage of which has appeared on YouTube.
They were protesting against planned EU measures to make new bike impossible to modify.
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