Where has that happened? In Australia it's been in force for the entire population for nearly 30 years, despite a few exceptions in court.
Google "Sue Abbott"
She is the Australian who appealed her fine for not wearing and the Judge upheld her appeal
''Having read all the material, I think I would fall down on your side of the ledger,'' the judge told Ms Abbott after she had spelt out her case against the laws that exist in few countries other than Australia and New Zealand.
''I frankly don't think there is anything advantageous and there may well be a disadvantage in situations to have a helmet - and it seems to me that it's one of those areas where it ought to be a matter of choice.''
He found Ms Abbott had ''an honestly held and not unreasonable belief as to the danger associated with the use of a helmet by cyclists'', and quashed her conviction, although he still found her offence proven.
Now Scone police ignore Ms Abbott as she cycles to town, although one yelled at her ''you're not in Paris now'' - a remark which prompted her to send police a photograph of herself bareheaded on a bike on the Champs-Elysees marked ''Greetings from Paris''.