Sound bites: zero-tolerance

http://www.nzherald.co.nz/section/story.cfm?c_id=1&ObjectID=10352222 Each time reference to "zero-tolerance" comes up, I wonder whether it's unlawful? In administrative law, there is a strong principle that a decision-maker cannot abdicate their discretion and adopt a rigid policy (see, for example, M v Syms, 5/12/1990 McGechan J & British Oxygen Co Ltd v Minister of Technology [1970] 3 All ER 165). That seems to be what be what is proposed with zero-tolerance - the prosecutorial "discretion" is being undermined and effectively subverted. However, traditionally the courts have also been reluctant to review the exercise of such discretion - but this seems to be changing (see Polynesian Spa Ltd v Osborne [2005] NZAR 408). Perhaps there is some hope in the future that we might be able to knock over this egregious approach to law-enforcement?