Not sure how but, they will find a way. A call to register for licence, or surrender the rifle/s? Perhaps, if the Police find a fellow in possession of an unlicenced air rifle, it could have serious consequences for him/her. The threat of a prison sentence will have an effect. But only for the law abiding citizen.
So it's the same old story then. Licence the law abiding citizens (ie the ones already in clubs and the ones with permission) while the ones who couldn't give a toss just carry on as they are.
Pretty much