Help Police

This sign has been here in Rose Street for a very long time and has bamboozled me for years.
Why advertise the fact that Police 'Regulations' not necessarily laws (local or otherwise) were required to be enforced, someone has gone to elaborate lengths to notify the local populance. I think it may well go back to when Rose Street had a much darker personality than the now pedestrian thoroughfare we presently enjoy.
I'd be most interested if any readers could come up with plausible explanation as like say it has puzzled me for years.