To mention: In Portugal it is technically not allowed. If you get caught with up to 10 "doses" of illegal drugs, not much will happen. But how much kava would be one time consuming (1 dose) for them?
It is funny, because I did my research there, and actually it is not allowed, but I found two online shops within portugal, that sell it anyway, but as whole root pieces (not worth the good price! I tried).
If you mind taking it with you, you could use an internet source and let it ship to a DPD shop f.e. (kavaeurope). And then you can be safe I guess. When the parcel arrives and is in the shop, you can collect it.