Anecdotally, as a college student in a state where marijuana is still extremely illegal, it is comically easy to obtain it while alcohol, a legal drug, is significantly more difficult to obtain (though still easy).

Following this pattern, from what I've seen psychedelics are relatively simple to get (albeit harder than weed), therefore legalization might actually make them more difficult to illegally obtain because dealers will be replaced by controlled medical practices in many markets.

Decriminalization will also open doors for people to study _how_ they affect the brain.