> The converse is also true, for example legalizing cannabis in Canada has significantly increased demand for it

The relevant thing that link actually says is that more survey respondents admitted to cannabis use after legalization, the obvious problem being that before legalization they would be admitting to a crime, which will suppress response rates.

The same link also points out that the legalization happened right before COVID and then you have a major confounder because even if cannabis use is actually up, you don't know if it's because of legalization or people turning to cannabis over stress from COVID. Moreover, the reported usage increased during COVID but started to decline in 2023. This implies that either the apparent spike was COVID, or that it was something like media reports about recent legalization acting as temporary free advertising and causing a temporary increase in usage. Neither of those is evidence of a sustained increase in demand.

Meanwhile legal options do cause people to prefer legal sources over the black market, and then you get fewer people becoming addicts because the thing they thought they were buying was spiked with something significantly more addictive by a black market seller. Or the black market products have higher variation in the dose and then customers can't predict how much they're getting and occasionally take more than expected, leading to a higher rate of overdose and stronger dependency-inducing withdrawal.

>Meanwhile legal options do cause people to prefer legal sources over the black market

In the case of cannabis it's been showing to lead to less underage use too. If it's a crime, then selling to anyone of any age is still just a crime. But if it's only a crime to sell to under 18/21 then legal shops will avoid selling to the under age to avoid revocation of their license.

> If it's a crime, then selling to anyone of any age is still just a crime. But if it's only a crime to sell to under 18/21 then legal shops will avoid selling to the under age to avoid revocation of their license.

That isn't true; crimes can have aggravating factors and selling drugs to a minor could aggravate the crime of selling drugs.

I don't think the laws were written that way, but they could have been.

There is an incentive to commit a crime when the benefit of committing the crime exceeds the penalty times the chance of getting caught plus the cost of measures taken to avoid getting caught.

This is why increasing penalties have extremely fast diminishing returns. As the penalty goes up, the relative cost of measures to avoid detection goes down, and the penalty needed to counter them becomes exponentially larger.

If the benefit of doing the crime is a million dollars and the penalty is a 50% chance of a year in prison then you have a problem, because plenty of people would be willing to take the risk. But it's actually worse than that, because spending $100,000 on countermeasures might lower the risk of getting caught to 1%, and they're still making $900,000. That might not be worth it when the penalty is a year -- maybe $100,000 in profit is worth a 50% risk of one year? But if you set the penalty to 20 years then it is. Then the gain is $900,000 but the expected penalty has actually fallen to 1% of 20 years, i.e. expected cost of 2.4 months instead of 6. To deter someone with a $900,000 profit who values a year at $120,000 with a 1% chance of getting caught, you would need the penalty to be 750 years, which you can't do because people don't live that long. And spending even more on countermeasures might lower the risk of getting caught even more. If spending $500,000 makes it 0.1%, that may not be worth doing when the max practical penalty is ~70 years, but the option for it means that even 750 years would be insufficient even if it was possible.

This is why there are things it's very difficult to deter. The profit from doing them is more than the cost of making the probability of detection small and then the size of the penalty can't be made large enough to be a deterrent.

That all changes when you legalize most of the market. Now the profit isn't a million dollars, it's $100,000, because anyone can enter the market so increased competition drives down margins. Moreover, $90,000 of the profit was from selling to adults. So now the profit from selling to kids is only $10,000. Not worth spending $100,000 to lower the risk of getting caught. And then you can easily assign a moderate penalty that acts as an actual deterrent.

That seems like the only sensible path forward, if you assume that the only lever a society can pull to make punishment harsher is “longer prison sentences”.

What if the penalty for selling drugs to kids was death?

It seems like that would change the risk/reward calculation pretty substantially.

Would it though? How different is that than life in prison without parole? There are plenty of people who, given the choice between ~$1M and a ~1% chance of the death penalty, are going to pick the money.

You could hypothetically try to make the difference in the penalties larger by making the penalty for selling to adults smaller, e.g. a $10 fine, so that there is minimal incentive to pay for countermeasures when selling to adults and thereby have them already paid for and in place when selling to kids. But then you're just de facto legalizing selling to adults and trying not to admit it.

>could aggravate the crime

For dealers this would mean almost nothing when the punishment for dealing already lead people to do things like get in shootouts with police.

Meanwhile legalization of some drugs has directly shown that it decreases youth usage.

> For dealers this would mean almost nothing when the punishment for dealing already lead people to do things like get in shootouts with police.

I think you're getting at something valid, but it isn't quite what you think.

The punishment for dealing drugs is, as I understand it, mostly applied to major distributors. In this sense, selling drugs wasn't a crime before anyway.

If you're too low-level for prosecution to be much of a concern, it doesn't take much to guide you away from fundamentally similar crimes where prosecution is a real concern.

Oh come on. Weed use and addiction has absolutely surged since legalization everywhere I'm aware of - US states, Canada, other countries etc. Use everywhere / anytime / as a part of daily life has been completely normalized, it's not uncommon to see people hitting a weed vape in the middle of a work day. Not to mention the potency is far higher and this has been normalized, so one incidence of cannabis use is essentially a mind-blasting wave of THC vs. a casual joint with friends. It would be as if you went from say 12% of Canadians having two beers after work to a fifth of vodka. That the median casual dose in 2026 would have the median casual user in 2016 literally incoherent is undisputed among any weed smoker today.

>The relevant thing that link actually says is that more survey respondents admitted to cannabis use after legalization, the obvious problem being that before legalization they would be admitting to a crime, which will suppress response rates.

Sure, except Canada had legal medicinal weed since 2001 and everyone was aware that police attitudes towards it were very lax. There were even technically-illegal weed stores that the Canadian government took years to shut down. The number of people that lied to a pollster because they thought that the government would get them was almost certainly minimal. The fact that the trend is pretty smooth before/after the boundary confirms this.

> The converse is also true

It isn't true, at least not as a hard and fast rule. Post-legalization changes in demand differ greatly per country. It completely depends on contemporary cultural factors of the country in question.

Your claim is far too open ended to interpret clearly.

A change in demand post-legalization can absolutely be highly variable across different countries/cultures, but unless you can demonstrate a country that legalized cannabis and saw a decline in demand, then your as of yet unsubstantiated claim does not refute mine.

No, all I need to demonstrate is a country that saw no significant increase, not necessarily a decline.

From everything I know, the US states as well as the Netherlands that all decriminalized it in the 70s didn't see local use increase in significant numbers.

Neither did it in Belgium who did the same in 2003.

And before you go "decriminalization is not the same as legalization", in the "Making drugs illegal does not eliminate demand, but it absolutely curbs it." is clearly about drugs that have not been decriminalized at all.