Is it permissible for a judge to rule against one of his parents in a Hadd or Ta'zir case, whether or not there are other judges, and is his ruling against them considered disobedience, or must he resign?

It is permissible for a judge to hear a case involving one of his ascendants or descendants and rule against them, but it is not permissible for him to rule in their favor. This is not considered disobedience to parents (ʿUqūq) or severing ties of kinship (Qaṭīʿat Ar-Raḥim). The jurists have reached a consensus on this, including what is stated in "Kashshāf Al-Qināʿ," "Mughnī Al-Muḥtāj," "Ash-Sharḥ Aṣ-Ṣaghīr," and "Majallat Al-Aḥkām Al-ʿAdliyyah." Furthermore, the judge is obligated to follow the laws and regulations in force in his country.