That's kind of a minimal measure, and already implemented to some degree in many places. Its effects are limited, and it's a cat and mouse game because there are so many subtle ways to advertise.
These are all just speculations - we can take a stance we prefer and expand it ad infinitum. Kind of pointless.
Ie I am pro legalization, and I can't imagine if society had proper education and precise dosing people would go and overdose frequently. Do you often see people who decide to drink 2 litres of vodka in one setting? We all know how bad idea it is without the need to walk that path. Also alcohol is one of few (if not the only) drug that actively increases aggressiveness in consumers.
Its proven numerous times all over the world that legal marihuana pushes away worse addictions, lowers the crime. Even ignoring the tiny details of bringing benefits to consumers (select of various strengths and non-harmful methods of application), bringing benefits to the state (taxation, control over what folks consume) and overall society - taking away massive source of income for organized crime.
At this point it just doesn't make any sense for a rational society to have weed illegal. Shooting in its own foot, ignoring reality of humans and all that.
Psychedelics is another group where at least active research in treatment of various psychiatric disorders should be actively encouraged by state. Potential is massive, by far the best area for improvement in otherwise pretty stale domain of medical drugs development (unless you consider drugging into oblivion anybody with issues with valium et co, which basically no expert does).
