I only know the Oregon laws, so here is a summary:
You can be nailed with intoxication laws for driving under the influence of any illicit drug (they require a piss test if they have reason to suspect it). But, if you are walking down the street blazed cops can't do shit unless you're a threat to the general welfare. Alcohol is the only drug you can get in trouble with after consumption. A parent can give only thier kids alcohol in thier own house, if that kid leaves the house he could be hit with a Minor in Posession by Consumption and his parents would have to foot the bills of any damage.