Here is an interesting way to nullify a federal law. The constitution says that all prosecutions of us citizens is to be done by a jury and in the state where the crime took place. There can be a state law that says that any citizen that finds another citizen guilty of what the state is trying to nullify then that person must do as much time in jail as the person they helped to prosecute. If they send someone to jail for ten years then they do ten years in state prison. This forces the jury to declare someone not guilty for that federal prosectution which will then nullify that federal law in that state.