I don't have any on hand, but I'm pretty there's been surveys showing teenagers in the US admit it's easier to get cannabis than alcohol. I know that was 100% true when I was in high school. All it took was a phone call to 1 of 10 possible sources who would then deliver it to your doorstep. Getting alcohol meant trying to find someone with an older friend or sibling willing to go out of their way, or driving to the sketchy part of the town next door and hoping that one liquor store would sell to you.

Still 100% true. I turned 20 earlier this month, it has always been easier to get cannabis than alcohol for me.

With even the same parallels that consuming marijuana while underage was illegal before and will be illegal after. You may as well publish articles about the effects of alcohol on underage brains (which is actually quite detrimental) as an argument for prohibition.

So what's the logic here? One dangerous substance is legal, so we might as well legalize additional dangerous substances?

The logic here is that studies about the effects of a substance on youth has no merits in a discussion about the legality of adult use. Studies about the effects on adults would be more relevant.

The legality of adult use makes these substances more readily available to children, so their health effects on children are relevant.

But it's the illegal one that's easier for children to buy. Drug dealers are already breaking the law, they don't care if the customer is 14.

Can you establish that marijuana is more dangerous than alcohol? If so, I'd be very interested to see your sources and metrics. If not, I'd be very interested to see a justification for why marijuana should remain illegal.

No, I cannot. But so what? Are you saying it is harmless? I don't care if it is merely less dangerous than alcohol.

I did not, and am not, saying that it's harmless. That would be ridiculous.

But if it's less harmful than alcohol, a substance which is legal for consumption and moderated by the government, why should it be illegal? What's your justification for saying marijuana should be banned for reasons of harm, when you can't establish that it's more harmful than more easily available alternatives?

Or are you also arguing that alcohol should be banned, as well?

Edit: To answer your initial question, the logic here is "One harmful substance is legal, thus other substances which are less harmful should probably also be legal".

I'm also Canadian, a high school teacher told me a whole bunch of students got suspended for selling weed brownies at school. He also said a girl got suspend for being drunk around the same time.

The law hardly matter in these cases, people do what they will do. If edibles are illegal kids will just make them at home.

Once you make the conclusion that whether or not it's legal has no effect on whether people will use it, then everything else falls out from there. It's easier for kids to get illegal pot than legal and that will always be the case.