Dilution

One method to legalize harder drugs (such as cocaine, MDMA, heroin, methamphetamine, etc) it to have them sold only in diluted form, in regulated drinks:

  • The dosage should be low enough that it's impossible to overdose without consuming at least 5 litres (which is impossible for any stomach to hold at once).
  • The drink should not be flavored or labelled in a way that appeals to children.

This is very similar to how any other food-chemicals are regulated. For example, there's a legal limit to how much caffeine can be added to soda; same with food colorings.