Last month we held Scottish Drugs Forum's annual general meeting and as part of the event we asked attenders, who represented a whole spectrum of stakeholders in the drugs field, whether there should be a debate on decriminalisation.

The overwhelming majority of that group agreed that there should. Recent procedural changes in Scottish policing are welcome and can help kickstart that debate.

As The Herald has revealed, officers will now issue on-the-spot warnings to people found carrying small but unspecified quantities of cannabis rather than report them to the fiscals for prosecution.

This is part of a wider overhaul of how wider petty offending is handled by the police and, of course, will only affect the least serious incidents.

We are at a historic crossroads in terms of enforcement and the legislative framework around drugs. The need for open informed discussion and a clear vision is obvious.

Of course, the changes to law enforcement on cannabis possession change little in terms of the final outcome – no legal proceedings.

They save the public purse and reduce bureaucratic administrative tasks for police and the fiscal service. This is the latest move in a long-term trend.

In the early 1980s it was possible to receive a prison sentence for the possession of small amounts of class A drugs such as heroin or cocaine but that would be unthinkable now.

But these changes perhaps also begin to resolve what is a growing, serious and dangerous anomaly in UK drug law.

The Herald: A library picture of a cannabis plant

The UK Government’s Psychoactive Substances Act will make it an offence to supply any psychoactive substance but possession of some new psychoactive substances, so-called legal highs, will be legal – with the proposed Act making no distinction on the basis of levels of harm.

It will therefore inevitably be the case that it will be legally possible, when the Act comes into force next year, to possess substances which mimic the effects of banned substances - cannabis, amphetamines, ecstasy, LSD and Valium - but that may be more dangerous than the substances controlled under the Misuse of Drugs Act.

This clearly begs serious questions about our overall model of controlling substances and suggests the need for there to be a root and branch review of our existing drug laws. If we are to have laws on drug possession, they should relate to the potential harm of a drug.

And we should not by accident somehow develop laws which reflect the class of the person in possession. We decriminalise the possession of cannabis but what about other class B drugs? The impression may be gained that cannabis use is viewed as not only more widespread but as crossing social classes more than the use of other substances.

The Herald: The cannabis factory in Eldon Road, Walthamstow.

Of course, no matter the legal status of drugs, people will get involved in problematic substance use. One only has to look at alcohol to see that legal status is not the only issue. The question is does criminalisation help people with problem use or reduce their number?

That long-standing question is beginning to be answered with the evidence base being generated by the development of a range of types of decriminalisation in over thirty countries including Portugal, the Czech Republic, the Netherlands and some US states.

These have shown some encouraging results in terms of linking people to treatment, avoiding imprisonment and reducing overall demand. There is also the reduction in the negative aspects of criminalisation. We know that the criminalisation of people who possess and use drugs marginalises and stigmatises them. This hinders access to social and healthcare services which could address their drug and other issues. Criminalising people affects their job prospects, family and other social ties. It is also hugely expensive.

Pressure on the United Nations in 2012 led to the decision to convene a UN General Assembly Special Session (UNGASS) in April 2016. The assembly will consider if ‘revising the approach on drugs maintained so far…can no longer be postponed’, and if the UN needs to "conduct an in-depth review analysing all available options’.

Secretary General Ban Ki-moon has urged members to use UNGASS ‘to conduct a wide-ranging and open debate that considers all options.’

This wide-ranging global debate should encourage Scotland and indeed the rest of the UK to have an inclusive open debate, which through appropriate leadership and courage, begins to articulate a vision of a way forward.

David Liddell, Director, Scottish Drugs Forum