>Rates of harm have decreased dramatically.

I question the measurements of harm, which I believe in the Portuguese case is in terms of diseases/hospitalizations/deaths. Everyone knows high-functioning people who have alcohol or drug problems, who will probably not show up in such measurements of harmful use, but who nonetheless suffer personal and family problems due to their habit.

Also, this article, though a little dated, seems to contradict your claim about drug use in the last 12 months.

https://www.npr.org/2011/01/20/133086356/Mixed-Results-For-P...

>While people reporting drug use over the course of their lifetime has gone up, somewhat significantly in the last decade in Portugal, people reporting drug use over the last 12 months of their lives has actually gone up only slightly.

And again, Portugal didn't have much of a drug culture to begin with. Where drug use is a much greater and ubiquitous cultural phenomenon, like in the US, it is very plausible that decriminalization would lead to significantly increased use.

> https://www.npr.org/2011/01/20/133086356/Mixed-Results-For-P....

There's not much point continuing the conversation if you're going to cite 6 year old radio interviews between journalists who don't bother to cite their sources.

Suppose it does - why does it matter? Why should society be in the business of policing what people put into their bodies, in their own homes?

The argument from freedom of agency isn't very convincing when drug addiction deprives you of free will itself.

Not all drug users are addicted (in fact, given the popularity of marijuana, I would say that the vast majority aren't). Indeed, many drugs on the prohibited lists don't cause addiction - or at least anymore so than, say, fast food.