i'd say the best outcome here could be obtaining a substance which contains unlisted research chemicals.
i could be wrong here, but i've never seen a synthetic cannabinoid blend with the active ingredients listed.
personally i see these chems as too risky, but that doesn't stop a lot of folks taking them. the problem is, it is hard to check (with any certainty) that what you are getting is truly "legal"
worst case scenario is that the package gets intercepted and found to contain a banned substance.
i'm not well informed about how the industry has managed to "stay ahead" of the legislation on this - by that i mean, there are many vendors claiming to be selling a legal product, but i have no idea whether this is true or whether they are simply gambling on it not being tested. the market seems to be profitable enough at this stage that such risks may seem worthwhile to the vendor? i can't be sure either way, but i am definitely dubious about the claims of legality.
would the vendor get busted as well? it's hard to say, because it would depend on a number of factors. if they're not discreet, then it would certainly seem possible. the state governments of australia have all acted on this industry in the last year because it was essentially operating openly under their noses for years without their awareness, and now that they've legislated to ban the various RCs used in making synth cannabinoid blends, it seems like the more publicised cases of interceptions/drugs charges the better, in terms of their message. i think there is pride at stake in regard to government and law enforcement, and it seems to me like the ship has sailed. i wouldn't want to be caught for buying something like that online, unless i was pretty confident is truly was legal.
frankly, this isn't a risk i would run. i don't know how quarantine varies from state-to-state, but i know that where i live (WA) there is a big focus on stopping plant/fruit/vegetable matter from entering the state. again though, it is hard to know how big the risk is, but sniffer dogs are frequently used to locate plant matter.
can you find a local vendor of the substance in question?
if you really want to go down the path of synthetic cannabinoids, this would be a much less risky proposition.