American Psycho

I think it should be legal especially if the material was farmed, which has been proven to drastically reduce poaching.

If it is old Ivory, and is decades old and has been in circulation for quite a while, then yes. If not, no

Well, is it harvested legally? Was the animal legally taken or poached.

I tend to say yes it should be illegal to be transported out of locale. Animals that produce ivory or bone used for making utensils and other commodities take years to reach maturity, so I think only the people living in the area should be allowed use it. High demands across the globe invites greed, which leads to possible extinction of the respective animal. On the other hand, I believe laws banning sales of antiques are useless and ridiculous. I inherited a piano (over a hundred years old), and when I brought in a tuner to fix the strings, he warned me to never try selling it because of laws governing prohibition.

Illegal. And the penalty for poaching should be death.

Should people who own ivory and other trophies be punished?

Depends if they got it illegally (It was obtained before poaching was made illegal)