Native possession only and not for sale, only for personal use.  The cultural carving heritage is preserved but the greed factor is removed, which as we've seen can drive unscrupulous types to result to poaching and worse in order to secure ivory.
Possession only by natives, trade only, not available for sale to anyone, native or white, and only within the communities allowed to hunt the animals that provide it.  It's the tourist trade driving the greed that created this situation and if we remove that temptation then there will be little reason for people to poach.