Any freedom in the physical world is always regarded in the sense of degrees of freedom. If by free will you mean an absolutely disconnected omnipotence, then stating the non-existence of such a concept of free will becomes a trivial and almost meaningless exercise. In any interacting system, the constituent degrees of freedom are constrained by each other through interactions. But to be constrained is not equivalent to be determined. I believe this to be the key issue to any meaningful discussion around the concept of free will.