It will be illegal to buy or sell any ivory without documentation of its age, which should be approved by the US Fish and Wildlife services. According to the International Fund for Animal Welfare:
That means no antiques, no bangles you bought at a market in Africa, no carved chopsticks. There are exceptions for household moves, museum or scientific specimens, instruments within an orchestra, and a few other non-commercial imports, but the rule of thumb is, if you’re planning to wear it, sell it, or show it off to your neighbors, it won’t make it past the border.
Ivory exports are now limited to proven antiques and a short list of non-commercial items that are still allowed.
Here is more information on how this affects the trade or movement of antique objects: https://www.antiquestradegazette.com/news/2014/us-include-antiques-in-ivory-ban/
More details on the consequences for antique dealers can be found here: https://www.washingtonpost.com/news/energy-environment/wp/2016/06/02/its-final-selling-just-about-any-item-containing-elephant-ivory-is-a-crime-in-the-u-s/