It depends, you could do it, but you might risk getting sued by whoever owns the copyright if they thought that you were breaking it. And in that case you would most likely be told to not do it or risk a lawsuit where you would have to argue your case.and you would most likely loose if its were clearly a copy. So as I said, you are NOT allowed to make a copy of his statue and call it "David 2", if its obvious that your intend is to copy it. But you could make a statue standing the same way with long hair, a slightly different body shape and call it Leonardo, I don't think there would be anything wrong in that.

I really doubt that they have a copyright on his pose, his hair, size of statue, material and whatever you can think of. Its a copyright on that particular piece of art.