You are not wrong Nigel we allready have adequate law in place to deal with the situation pressure should be directed to the police to do the job.
Some years ago a Man in Farnborough made a cardboard notice warning motorists about a local speed radar operation conducted further along the road, one of the officers went along to him telling him to not warn of the trap conviscating his sign in court subsequently he was fined & had points added to his driving licence for the misdemeanor.