IT could be a pub quiz question. What do Armenia and Argentina have in common? The Czech Republic and Chile? Paraguay and Poland? The answer isn’t football. Each has decided, in some fashion, that if you just say no to drugs, you say nothing useful at all.

Depending on the definitions used, there are between 25 and 30 such countries. Their laws, methods, aims and ambitions vary. Some have legalised drugs. Some have “re-legalised”. A few never got around to prohibition to begin with. Most have experimented – for personal use, you understand – with a gateway policy, decriminalisation.

Last week the Republic of Ireland decided, in effect, that what’s good enough for Belgium, Spain, Portugal, Estonia, the Netherlands and others might help with its own liberation from the half-century of failure we still call, without irony, the war on drugs. With a leaked report suggesting that the UN Office on Drugs and Crime (UNODC) is on the brink of advocating decriminalisation, Ireland joins a growing consensus.

Britain doesn’t want to hear about that. Or rather, the Conservative Government doesn’t want to hear the accusation “soft on drugs” from its press sponsors. Amid a fragrant haze of hypocrisy, the line is that there will be no change, funding cuts aside, in UK drugs strategy. Meanwhile, police forces the length of these islands are improvising policies of their own.

In Ireland, serious thinking has been going on. The result, if carried through, will be the decriminalisation of drugs in “personal use” quantities combined with the introduction of injection (“consumption”) rooms. Narcotics will remain illegal, but in future – or such is the hope – no-one will be treated as a criminal because of an addiction or a problematic habit. The Irish are making a fundamental distinction.

Officially, Britain remains tough, tougher than tough, on drugs. Unofficially, an ad hoc pragmatism guides enforcement. A fall of close to a third in cannabis possession offences in England and Wales between 2011-12 and 2014-15 has not happened because dope has lost its allure. With budgets cut to ribbons, police forces have concluded they have better things to do than harass cannabis users.

There are worse principles a government could apply. In a speech at the London School of Economics last Monday, Aodhain O’ Riordain, the Irish minister responsible for drugs strategy, maintained that a “cultural shift” is required. Addiction should be regarded as a health issue, he argued, both for the sake of individuals and for the benefit of law enforcement. Time and money spent hunting addicts could be better used against a criminal trade.

O’Riordain advocates decriminalisation, not legalisation. He is not alone in that, though at the LSE he failed to explain the logic. Portugal’s experience over the last 14 years is the Irish minister’s inspiration, as it is for many reluctant conscripts in the war on drugs, but a conspicuous Iberian success remains half an answer to a complicated question.

With Europe’s highest HIV infection rate among injecting drugs users, Portugal faced an undoubted crisis at the turn of the century. Desperate, it decided that drug use or possession should remain offences, but not criminal offences. The money spent on treatment and prevention was doubled. The police meanwhile began to ignore mere marijuana use. And the HIV rate started to fall.

It has not been plain sailing since. According to some studies, hard drug use has increased. More people have sought treatment, perhaps as a result, but the number of drug-related deaths has declined. Pressure on courts has eased, meanwhile, and the street price of drugs has fallen. Adolescent use seems to be waning, but with the police still seizing several tonnes of cocaine each year, the effect of reform on organised crime has been hard to measure.

That, though, is an aspect of decriminalisation too often overlooked. On its own, without a wider health policy or O’Riordain’s “person-centred” strategy, it does not “solve” a narcotics problem. Chiefly, it spares individuals the brutal effects – prison, stigma, unemployment, existence without treatment or medical care – that are legacies of the unending war. But decriminalisation alone is not enough.

It counts as a start, nevertheless, and that is more than Britain has managed. Last October, the Home Office caused strife within the coalition by publishing a report, Drugs: International Comparators, that looked at the experience of Portugal and a dozen other countries. To the dismay of Tories, the survey said there was “no apparent correlation” between tough laws and the level of drug use. While decriminalisation would not curb use, there were “indications that decriminalisation can reduce the burden on criminal justice systems”.

Who’d have thought? In the ensuing battle, the LibDem Norman Lamb resigned as a Home Office minister while policy – “this government has absolutely no intention of decriminalising drugs” – was reaffirmed. Faced with a problem, Britain had not got beyond failing to put two and two together.

Why decriminalise? For an Irish recreational user, far less an addict, the question is superfluous. Nevertheless, O’Riordain, like his peers around the world, has taken a first step and refused the second. As the Home Office report suggested, decriminalisation has little effect on use. People go on buying their blood-stained substances and enriching some of the nastiest people on the planet. A few more police go to work hunting traffickers. Users are no longer persecuted. The mafias remain.

In 2006, the Italian journalist Roberto Saviano published Gomorrah, an expose, in the proper sense, of the Neapolitan Camorra. He has been forced to live since under armed guard in secret locations. Nevertheless, this summer he published Zero Zero Zero, a title derived from a traffickers’ joke name for pure cocaine. The book is horrifying, but not just for the routine, fantastical violence. In Saviano’s account, the cartels’ trade has corrupted the world.

UNODC will mention “vast sums” that “compromise” economies, buy politicians and rig elections. Saviano will tell you that drugs money courses through the world’s financial systems, that it touches all of us, and that it alone kept banking afloat in parts of the Americas during the great crash. He calls it narco-capitalism.

The journalist has dedicated his life to opposing the mafias. Nevertheless, in the last pages of Zero Zero Zero he writes: “As terrible as it may seem, total legalisation may be the only answer. A horrendous response, horrible perhaps, agonising. But the only one that can stop everything.”

That strikes me as true. By one calculation, the United States alone had spent $150 billion on the drugs war by 2010. Any victories? Or just the news that Barack Obama has been commuting sentences on dozens of hapless souls locked away for life because of recreational use? According to the Federal Bureau of Prisons, as of September 26, 48.4 per cent of the entire US inmate population, 93,821 individuals, had been locked up for drug offences. Some war; some victory.

So legalise the lot. Those who want to use drugs will go on using drugs. In a country with common sense, like Ireland, they might get the help they need. But Saviano is right. Only one thing will put the traffickers out of business and end this hopeless war.