The impression I have is lawmakers are worried about making a law which is too wide sweeping and stifles what they define to be legitimate medical and biological research, hence the clause in the american analog law mentioning intent of human consumption and similarity in the activity of an already controlled substance. They would either have to greatly expand the number of licenses given to work with controlled substances and by implication the amount of oversight or make the law more specific in exactly who and what it is referring to. As we all know, there's a number of problems for law enforcement and prosecutors with regard to the american law and a large number of very recreational compounds which would be hard to prosecute under the american law, but it's really the only approach I can conceive that a government can go and still have a broad coverage while not bringing too much burden on researchers who do not test the substances in man. One thing that has confused me about the american law is, if a substance that is psychoactive but not known to be psychoactive is sold, even if it is an analog of an existing compound, but has no published scientific research detailing its en vivo action and is not sold as having such an action, does the substantially similar effect clause only apply to substances known to have this effect? It would seem that research about the psychoactivity of the compound in question would have to be conducted before a prosecution could be successful.
6-apb for example has no mentions of psychoactivity in any of the available scientific literature, and the only mentions remotely relating to psychoactivity are in Lilly's patent application for the compound mentioning 5ht2c agonism, and I could be wrong but I don't get the impression that 5ht2c agonism necessarily translates into psychoactivity.