Yeah, there’s some truth in that. But there is also a justification (predicated on prior justification for existing hard drugs being made illegal). The justification is that it is not difficult to synthesize similar drugs that have similar effects. And very often, the differences in the effects are such that the new drug is more harmful than the drug it is copying. So rather than just automatically allowing every new drug and then playing an never-ending game of wack-a-mole with new and dangerous addictive drugs, they are just automatically banned.

There are a lot of arguments for why it might have been a mistake to make certain drugs illegal in the first place; but that’s a different issue. If certain drugs are harmful enough to be illegal, then it is definitely justifiable to make similar new drugs illegal by default.

A similar thing can apply to weapons. We don’t usually have laws against specific make and model of weapons. The laws are usually for entire categories, which include new versions are not yet created or tested.