illegal ∈ regulated
> Drugs are not regulated but are illegal
Drugs are strongly regulated (ask your pharmacist) AND some of them are strongly regulated AND are also illegal
Illegal by definition means that there was a regulation that created this status. Those drugs would be alegal otherwise.
Regulated means that for some special cases the use is allowed, even if is not ok for a recreational uses. A physicist can have solid reasons to give a morphine derivative to somebody in a perfectly legal situation
So they're not exactly illegal.
Some other classes of drugs are totally illegal for use in humans. (Limited to research only with extra hoops.) Not opiates.
Examples include: LSD, MDMA (changing), PCP, Psylocybin, Psilocin, Muscarine, a bunch of chemically similar drugs and a few other hallucinogens.
THC and CBD were in this class and are now legal in some countries and states of USA.