Yes, exactly. You are suppose to have any ivory you use documented by a licensed reseller. Whether someone would come after you for a few guitars you make is questionable, but if they did the fines are bad and jail time is possible. How much do you have? How many guitar would it make?
I use Mamoth ivory myself and I keep documentation on all of it.
Old ivory though is GREAT stuff. Naturally yellowed. Beautiful. You can cut, sand and glue it just like any other material you use. But, it doesn't smell that good.
All elephant Ivory that is currently in the country is assumed to be pre-ban. The burden of proof is on fish and game. The only Ivory seller license that I know of is from New York, I have one, but I don't sell Elepahnt Ivory anymore since it is very illegal in California since 2007. There is even an 'illegal to posess with intent to sell' clause in the penal code. It is also illegal to import into California. So, I also only use and sell Mammoth Ivory now. It could be implied that a guitar that has any elephant ivory on it cannot be brought into California, even to return from vacation!
The true authority on this is David Warther, of IvoryBuyer.com.
-James Leonard