Truth is, I think that as long as its a personal item and not intended for resale, then you should be ok. But how can you really prove anything? And, I've tried to use the pre ban argument in the past with no luck. All the per an paperwork stays with the original purchaser, so it could be with the cue maker or even worse, the supplier that the cue asker buys his ivory from. And there is no way to prove that a particular ivory inlay came from a particular legal batch without physically removing the specimen to be tested (and I've had this happen to me) and removing means destroying. I had a cue get hung up at US customs because of a pressed pig skin wrap that the clever agent thought was banned monitor lizard. The only way to get my cue through was to let them remove the wrap, destroying it by the way, to have it tested. Then when it tested to be pig skin, I got my bare naked cue and torn up pig skin back with no sorry or reimbursement. Don't know as much about the Japan side, but the US side is allowed to do pretty much anything they want with absolutely no liabilities as long as they suspect something to be wrong.
Dave