Gloucestershire Police has said officers will pull over any cars they think are making unnecessary journeys out of Wales as residents there go into another lockdown.
The force confirmed drivers will be stopped if it is suspected they have driven into England without a justifiable reason.
Officers will advise anyone caught to turn around and, if they refuse, Gloucestershire Police will report the incident to police in Wales who can then issue fines.
It is being done to help Welsh authorities crack down on any non-essential journeys while the country enters a two-week firebreak lockdown.
It forms part of a wider police operation in response to the high numbers of people from outside the Forest of Dean area visiting Cannop cycle centre and parking on grass verges nearby.
A spokesperson from Gloucestershire Police said: "While we cannot issue fines to those travelling from Wales into the county we can inform the host force of those we stop about what has happened so they can take action.
"Officers will be running an operation from tomorrow [24 October] and over the weekend that will cover routes from Wales into the Forest of Dean and if we stop someone travelling from Wales we will be encouraging them to turn around if we are not satisfied with their explanation."
The force stressed that most people are following the rules, but will take action if some are flouting them unnecessarily.
Wales' 17-day lockdown started on Friday.