Perhaps a better strategy would be to order anybody caught in possession of a knife..... if not convicted of any crime..... to attend an education course specifically designed to, well, educate on the risks and dangers, and the alternative options. They would then have to sign a register that states they agree to no longer carry knives. They will remain on that register for five years and if caught in possession during that time, they will then be convicted under laws passed to cover such eventualities.
That's a good idea