Those are very good questions about the MMPA.

What I have read up on is the ban within the USA of buying, selling, or possessing ivory "worked or unworked".

The USA ban is distinct from CITES and much stricter. The USA ban isn't a law, it's an Executive Order by President Obama. I haven't heard if it has been rescinded after he left office.

It has complex rules concerning exactly what ivory articles are legal. You have to be able to document that the ivory was gathered "from the wild" before a certain date AND that it was within USA borders by a certain date AND that it was in your possession before the ban took effect.