Outlawing Synthetic Marijuana: What is the Target?

The legislature in Virginia has banned synthetic marijuana, manufactured substances that are not pot, but when smoked induce similar effects. Things have gotten difficult because manufacturers stay one step ahead of enforcement by changing the formula.

"It seems that once a compound becomes prohibited, the people who are manufacturing these preparations just take that compound out because it is prohibited, and they now add in another one that is not," says Department of Forensic Science Chemistry Program manager Linda Jackson.

My question is what is the target here? On the one hand, it is the substance and not the effect of ingesting it. Alcohol makes you intoxicated, marijuana makes you intoxicated. Alcohol is legal, marijuana is not. So, it is not the intoxication, but the substance that seems to be the target for elimination.

On the other hand, in the mind of the authorities, by changing the chemical make-up of the synthetic pot, it does not become a new thing, but is still the same thing they sought to outlaw, synthetic pot. But how can two different things be the same thing? This makes sense if the substance is not the issue, but the effect of it. Both chemical substances cause intoxication and so are functionally identical despite being chemically distinct. So, here it is the intoxication that they are trying to eliminate, not the substance.

So, exactly what is it that they are seeking to eliminate? What is the target?