Alcohol, tobacco, and deep-fried Twinkies also have negative health effects. In a free society, does government or the individual adult decide whether to self-inflict those negative health effects?
I will rephrase your question to: “Does the Government have the right to prevent you from harming you in your pursuit of (?) pleasure? (I would not say happiness In this case.)
I was not really attempting to answer that question. I did provide a resource to assist people with information on why marijuana is not a harmless recreational drug. It is good that people have access to this information, is it not?
I will ask in return; should some one be allowed to use methamphetamine even once? Or heroin? With addictive drugs you may choose to use it the first time, but do you really have free choice after that? Do you wish that freedom on someone who ends up a prostitute or a career criminal to support their habit? How free is the person whose home is burgled by someone to support their habit? A law does not provide absolute restraint, but it may make someone think twice before taking damaging action.