The law of causality is ultimately incompatible with free will. You cannot have truly autonomous agency within a physical framework ruled by cause and effect. To truly express freedom of will, without influence from any prior cause, you would literally need to exist in your own isolated vacuum of space and time (no outside influence from environment), having also created yourself (no outside influence from genetics). That is to say, if you believe you have free will, the burden is on you to prove that your body, and your brain itself, are not bound by the laws of the physically causal universe.