John in NM
As I understand it, a chair can be patented - using a design patent rather than a utility patent that might be used for a piece of machinery.

Copyright applies to non-functional objects, in some cases furniture (I saw a concrete barcalounger once )....

How trademark fits in there is beyond me...

The problem however, is not the protection provided by law, it is in proving infringement. I've had the misfortune to inherit a lawsuit that concerns a fairly simple breach of an unambiguous contract. It has dragged on 5 years now and the outcome is far from certain. While the law is clear and specific, proof of breach and responsibility for damages can be quite difficult to prove.