not sure how much ivory is used in guitars (nuts or fretmarkers?) but if you have it, read on...

vale

https://www.theguardian.com/world/2018/jul/29/new-zealand-ivory-keys-imported-antique-piano

"will have to fit expensive synthetic tops to the keys, intends to fight the government order that he also pay for the removal and dumping of the ivory."

Branshen

Absolutely horrific. 

Funkfingers

Sledgehammer to crack a nut. 

• The bureaucrats presume that animals were killed specifically to obtain their ivory. 
• Source certification is a relatively recent thing. Difficult to prove either way on old materials.
• Destroying old objects is not going to bring the dead animals back to life.
• The African elephant is almost certainly doomed to extinction anyway. (Habitat destruction.)
• The best that denying access to ivory objects in the present can achieve is to reduce the desire of individuals to acquire it in the future.
• Human nature being what it is, people will still endeavour to possess stuff even after it is made illegal to do so.

Roll up. Get your Novichok here. Edvard Munch paintings available on request. Frames extra! 



Back on topic. Ivory might occur in bindings or as a nut. I associate its use more with the lute. 

Whitecat

This should be a cautionary tale for any CITES I material - which includes Brazilian rosewood of course.