Members are advised to review legal restrictions applying to their jurisdiction when offering or acquiring items that incorporate such materials as ivory or rhino horn.
At the US national level, here is a brief review of restrictions to import, export and interstate trade: Can I Sell It?
Further analysis of state level restrictions may be found at: Understanding Ivory Lay
In my personal opinion, CITES was very poorly implemented by the US and the rash of recent laws and regulations concerning such trade of antiques within the US are very unlikely to serve the legitimate purpose of saving any wildlife. But, if you are caught violating any of these laws, the governments can and will hurt you.