It's prohibited to import kava for commercial purposes... It's also prohibited to import it to drink it, but explicitly legal to rub it all over yourself (anybody tried this? lol). Seeing as there is no way for a customs official to know what you are doing with it, you can import it. If I hadn't seen Ed's photo above (can I call you Ed? what about Eddy Baby (Monty Python quote!)) I would have said large quantities would get stopped.
I can see why Ed (I'm calling you Ed) would have large stocks. If this got popular here, it would be banned in an instant. We have some wonderful outlets of journalism over here (the daily mail, the sun, the telegraph) who would jump on the chance to demonise a group of people who weren't obeying their societal norms.