As an amateur woodworker, it is hard for me to know the true source of wood that I buy. I am aware of CITES and the well known woods that are endangered, so I try to behave in a responsible manner when it comes to acquiring wood.
I buy some wood at lumberyards and woodworking stores, and I trust that they follow the law and regulations as it goes through the supply chain to them.
A lot of wood comes from woodworking club members. Sometimes they "retire" and the club helps their spouses sell off their accumulated materials. It is impossible to know the provenance of wood from those sources. I see endangered woods among those collections, but must assume they were harvested in a responsible way. More likely, they were harvested irresponsibly, but before people understood the implications of what they were doing, and before CITES was more widely known and understood.
I have seen rare, endangered woods for sale on the internet. I suspect that they are the result of illegal harvesting, and personally avoid them. Among other things, I make pens, where small pieces of rare, exotic woods are popular. Pen blanks are small, and it would not surprise me to learn that the huge popularity of pen making along with the small piece size encourages illegal harvesting and smuggling. By smuggling, I mean eBay purchases from overseas, for example. I see a lot of pen blanks for sale on a pen turning website, and I suspect that some of it was illegally harvested. The sale process is informal, with PayPal on one side, and ordinary mail on the other. With rare exceptions, I don't buy from them unless I am certain I understand the source of the wood.
I admit to having a few pieces of woods from endangered species. I got them all from the families of deceased woodworkers, and can only hope that they acquired them responsibly. The trees were already long gone, and it doesn't make sense to destroy those pieces. I suspect that most of the pieces are decades old. If I had not acquired them, then other club members would have picked them up. I keep them safe and hope to find the perfect use for them someday. You can call it irresponsible. You can call it reasonable behavior. You can call it privilege or rationalization, but it is what it is.
I freely admit that I do not have all the answers. I am willing and eager to see other points of view. I hope others contribute suggestions or recommendations for better approaches to those gnarly issues.