Note: the pardon potentially isn’t really the big news, directing DOJ and HHS to reexamine the scheduling of marijuana under the Controlled Substances Act is potentially a much bigger deal going forward.
It seems pretty clear that psychedelics and entactogens (LSD, psilocybin, MDMA, 2-CB, etc.) have totally different characteristics than "these will ruin your life" drugs like heroin and fentanyl. A sensible drug policy would recognize those differences.
I've never been a fan of drug control, but the scheduling system is particularly absurd. Drugs that are widely consumed without negative connotations for society shouldn't be cause for imprisoning people.
By far the most harmful drug was alcohol. I might be confabulating, but IIRC some government officials in the UK even asked some of the researchers to downplay some of their findings, because it basically showed the ridiculousness of government drug policy.
Regardless, though, the details of the report itself are worth a read, as I think they fairly assessed harm across different criteria, e.g. harm to oneself vs. harm to others.
https://www.thelancet.com/journals/lancet/article/PIIS0140-6...
I think this chart that's linked on Wikipedia[0] that's from this study[1] is more accurate, alcohol is still near the top of the list but heroin, crack and meth are still higher.
[0] - https://en.wikipedia.org/wiki/Recreational_drug_use#/media/F...
[1] - "Development of a rational scale to assess the harm of drugs of potential misuse" https://www.ncbi.nlm.nih.gov/pubmed/17382831
Not without legislation. The classification system is fixed in legislation, where things fall in it has some leeway (subject to treaty obligations, which are also sometimes problematic in this regard) by executive action.