Once again confusion caused by treating apples as oranges.
Saying marijuana should be restricted to medical use to protect children mixes two separate issues.
Marijuana consumed by adults gives pleasure as well as being therapeutic. More than can be said for alcohol, although an uncle of mine was told to have one glass of brandy a day and smoke a cigar to help his heart. He thought one good, more better and drank a bottle a day with his ten cigars for the next twenty years. I digress.
Controlling access by children is a separate issue and can be treated like alcohol by regulating purchase age, it won’t be perfect but will impose a measure of control, dependent, like with alcohol, on the level of enforcement, not on whether laws on prohibition are present.