I'll assume you exclude drugs like aspirin, antibiotics, and other run-of-the-mill medically approved pharmaceuticals. Our language is really inadequate in this area. There are also many legal and oft abused "medically approved pharmaceuticals" (like Oxycodone).
Even within the (currently) 'illegal' drug categories there are vast differences being lumped together.
My legalization interests lies primarily in the group of chemicals that are profoundly mind-manifesting and consciousness altering (each of which requires individual consideration and treatment as to how it should best be legalized and regulated - some only under a doctors supervision, others available to all adults).
My thoughts are roughly:
all adults, similar to tobacco/alcohol, self-grown, small collective or licensed small commercial. Encourage vaporization/ingestion over smoking
all adults, licensed producers, medical-grade, limited availability - possibly require medical approval
- Psilocybin/Mescaline/LSD/n,n-DMT/5MeO-DMT/Ayahuasca/salvinorian A:
prescription, medical-grade, under controlled circumstances but not doctors care (I envision 'trip centers' where people can go have safe experiences under educated supervision, eg, Ayahuasca contains an MAOI, so there are dietary and drug interactions to be careful of, but millions of people take it safely every year throughout the Amazon basin)
medical-grade, only under doctors care & supervision, something like 1/year recreational limit unless medically indicated (e.g., for opioid-addiction treatment)
Those are the ones I think can profoundly help mankind should we choose to use it properly -- all have indices of harm far below alcohol and tobacco and all are profoundly different from most other illegal drugs.
And, while I don't advocate that methamphetamine be made fully legal, it should be legal and available for researchers and if medical applications are found we have no business or interest in blocking them. Doctors educated in the field are the ones in a position to make those judgements. And it should not be a criminal violation to be caught using methamphetamine -- it should be an intervention, medical and psychological care should be given to the individual, they need help not imprisonment. All imprisonment is going to do is ensure that their life is utterly destroyed and give them no path to get back on their feet, which often destroys their families far more profoundly than the drug abuse itself.
Addicted individuals should also be given treatment even if that means the BEST we can do is give them a safe source for their drug of addiction and a safe place in which to use it -- but this treatment should be medically determined on an individual basis.
The illegality of cannabis is outrageous, an impediment to full utilization of a drug which helps produce the serenity and insight, sensitivity and fellowship so desperately needed in this increasingly mad and dangerous world. - Carl Sagan