For future reference, please use code tags when you post code on the forums: Using code tags properly
Right now your code will only call that method if one of the mouse axes is not zero. I’m not sure that you need anything with ‘else’ (or even have else at all, rather).
If your camera is still rotating when you’re not moving the mouse, I suspect that the method is being called elsewhere, or its rotated by a parent or some other means.