Your missing the point. Is the Saudi government a murtad government for deriving the laws of driving a car from a kafir country? Anothe example, are the Afghans murtad for following their tribal law "Pashtunwali" ?
Your differentiating of following and legislation is meaningless. If the following of the law is not disobedience then how does legislating it suddenly cause disobedience? Either the law is Kufr or it is not. Obeying in matters that cause disobedience to Allah is not permitted even in muslim country let alone a kafir country. Nor is anyone preventing you from migrating, that you can claim to be "forced".