There are a handful of things I do to try to insure no future problems. Getting the moisture content stable in my wood and keeping it stable is a start. Only a decade or two will tell how successful my way of doing things is though.
I did a little research concerning the interstate shipment of ivory. One place says that the shipping of endangered species from state to state is prohibited. This usually means any part of such an animal and Asian elephants are classified "endangered" I believe. Further down in the same paragraph it states that CITES legal African ivory can move freely within the US. As far as I know, there has never been an issue with the movement of legal ivory from state to state. Please do update me if you know of problems with any specific state or border. I try to keep up with such things.
Hu
(included text, I highlighted the parts of primary interest)
The U.S. Endangered Species Act lists the Asian elephant as "endangered" and the African elephant as "threatened." The Endangered Species Act prohibits the import and interstate commerce of products of all species listed as endangered. Additionally, the African Elephant Conservation Act, passed in 1988, allows the U.S. government to take strict action against illegal ivory imports and authorizes government funding for elephant field conservation projects. Under this law, the U.S. banned imports of African elephant ivory in 1989. Within the United States, however, it is legal to buy, sell, and transport African elephant ivory that was purchased before the ban. It is not always clear, though, how this determination is made as there was no obligation to report and register such stocks at the time the ban was imposed. Both CITES and U.S. law allow for limited import of noncommercial sport - hunted African elephant trophies and elephant hides from certain countries.