But my understanding is your employment contract can pre-assign that property to your employer, and that contract will be enforceable in (e.g.) California if th

But my understanding is your employment contract can pre-assign that property to your employer, and that contract will be enforceable in (e.g.) California if the IP relates "at the time of conception or reduction to practice of the invention to the employer's business, or actual or demonstrably anticipated research or development of the employer". (IANAL; TINLA)