AS officers know well, it is not for the police to shape laws on drugs. There might be a ready audience for another debate over the decriminalisation of cannabis, but that is not, strictly speaking, the business of Police Scotland. Instead, the force is preparing to ask important questions of its own.

Where petty offences are concerned, those could be summarised as what, how and why? If the offence involves an individual caught in possession of a small amount of cannabis for personal consumption, what should an officer do? As things stand, the issue of “how” follows, given the high chance of a report to the Crown Office leading to no action. Hence the inevitable: why?

For police and prosecutors, all this is an endlessly frustrating waste of time and resources that could, self-evidently, be better spent. When around 45 per cent of offences fail to justify prosecution through the courts, there has to be a more sensible way to proceed.

Equally, police cannot lose sight of the public will. Urinating in the street counts as petty to all save those who suffer the consequences. It cannot simply be ignored. Discreet cannabis smoking might have no effect on anyone save the user. Parliament has nevertheless deemed it a criminal offence. A nod and a wink won’t do.

We have reached the point, nevertheless, at which common sense becomes imperative. Recorded Police Warnings are unlikely to appeal to those who subscribe to the myth of zero tolerance, but they are a rational response. Even those wedded to a war on drugs should ask themselves which they prefer: officers filling in pointless reports, or serious narcotics investigations.

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Next month’s changes involve deeper considerations than the alleged toleration of cannabis. Implicitly, police are asking us to wonder why they – highly-trained, forever overstretched – should be left to deal with the wandering alcoholic, the disturbed shoplifter, or the youth urinating in the close. Too often, such policing amounts to improvised social work. When the offences are too petty to trouble the courts, the exercise is futile.

The new warnings should also help to fix an old problem. Hitherto, the range of possible responses to petty offences has failed to meet the definition of proportionate. One miscreant might have suffered a fixed penalty notice; another, caught for the same offence, could have earned no consequences. Equally, the use of “adult police warnings” has revealed old, pre-merger habits. There has been no consistency across the country.

Welcome as the new system is, a few questions arise. One involves the Lord Advocate’s confidential prosecution guidelines. If police discretion is to be exercised, there needs to be more transparency. What is a “small amount” of cannabis? And what harm is there in telling the public?

Equally, there is the wider issue of petty offences and the effort demanded of police. A vast volume of their work involves the minor infractions of motorists. Of all the demands on time and resources, that one truly invites the question: why?