Are these consenting adults going to accidentally harm/kill other non-consenting adults/children when they decide they can drive a car, for example?

If yes -> that's what some people have reservations not necessarily about legalizing drugs, but about making them more accessible (i.e. buy it at CVS or a gas station)

If no - > what about alcohol? That's a legal drug that impairs people and even though driving drunk is illegal, it doesn't stop thousands of people from doing it and killing tens of thousands per year