I think your reference to the NRA is a bit misleading in this case. The NRA had similar concerns as people who repair and sell used pianos. That is there is a large existing inventory of guns and pianos that use ivory. A total ban would make criminal many otherwise innocent transactions.

See:

https://www.nraila.org/articles/20140305/ivory-ban-fact-shee... http://www.ptg.org/scripts/4disapi.dll/4DCGI/cms/review.html...