@hue-man,
Going back to the original statement:
hue-man wrote: I personally believe that selling substances that can cause harm to a person is morally permissible as long as the consumer is aware of the potential risks.
I think we've modified this, removing "is aware" and replacing it with "knows". I think regardless of age, you don't sell something to someone that they could hurt themselves with unless you have reason to believe they can handle it; that they know what they're getting into.
How does that hold up to the examples provided?
- Drugs to a 12 year old--too young to really make decisions based on risk
- Suicide--euthanasia vs teenage depressive seems to be drawn down the "know what they're doing" line, yes?
- Mildly harmful/recreational--warning labels and education suffice
- addictive--how does anyone know before hand what the addiction will be like? I think a strong argument could be made for not selling highly addictive drugs to someone who isn't addicted.
Of course, the "is it morally permissible for you to personally sell" is different from "what drugs should be illegal", because that has to keep matters of practicality in mind.