There is no doubt that Allaah has enjoined upon His slaves to rule according to His sharee’ah and to refer to it for judgement, and He has warned against ruling by any other laws and has stated that this is the characteristic of the hypocrites. He has also stated that any rule other than His rule is the rule of Jaahiliyyah (ignorance) and that there is nothing better than His rule. Allaah tells us that people do not truly believe until they refer to His Messenger (peace and blessings of Allaah be upon him) for judgement in all disputes between them, and find in themselves no resistance against his decisions, and accept (them) with full submission. In Soorat al-Maa'idah Allaah tells us that ruling by anything other than that which He has revealed is kufr (disbelief), wrongdoing and evildoing. All these things that we have mentioned here are clearly stated by Allaah in His Book.
With regard to those who study and teach man-made laws, they fall into different categories:
Those who study it or teach it in order to understand its real nature, or to understand the superiority of sharee’ah to these laws, or to benefit from it in ways that do not go against sharee’ah, or to benefit others in such ways. It seems that there is no sin on the one who does this, indeed he may be rewarded for that if he seeks to expose its faults and demonstrate the superiority of sharee’ah. The ruling on people in this category is the same as the ruling on those who study the rulings on riba and the various kinds of alcohol and gambling, and false beliefs, or who teach about such matters so that he may know them and the Islamic rulings on them, or he may inform others of that, whilst also believing that they are haraam, just as those in this category who study law believe that man-made laws which go against the laws of Allaah are haraam. They do not come under the same ruling as those who learn or teach witchcraft and the like, because witchcraft is haraam in and of itself, as it involves shirk and worship of the jinn instead of Allaah. So the one who learns it or teaches it to others only attains it by means of shirk, unlike the one who studies law or teaches it to others, not because he thinks that it is permissible, but for a permissible or Islamically prescribed purpose, as stated above.
Those who study law or teach it to others in order to pass judgements thereby or to help others to do so, even though they believe that it is haraam to rule by anything other than that which Allaah has revealed. But their desires or love of money makes them do that. These people are undoubtedly doing wrong and they are committing kufr, wrongdoing and evil, but it is minor kufr, minor wrongdoing and minor evil that does not put them beyond the pale of Islam. This view is well known among the scholars. It is also the view of Ibn ‘Abbaas, Tawoos, ‘Ata’, Mujaahid and a number of the earlier and later generations, as was stated by al-Haafiz ibn Katheer, al-Baghawi, al-Qurtubi and others. The great scholar Ibn al-Qayyim (may Allaah have mercy on him) also mentioned something similar in his book Kitaab al-Salaah. Shaykh ‘Abd al-Lateef ibn ‘Abd al-Rahmaan ibn Hasan (may Allaah have mercy on him) wrote an excellent essay on this topic which has been published in the third volume of al-Rasaa’il al-Oola.
Those who learn and teach man-made systems of law are likened to those who learn about different kinds of riba, alcohol and gambling and teach them to others for some whims and desires of their own or because of their greed for money, even though they do not regard that as permissible. They know that all dealings involving riba are haraam, just as they know that drinking intoxicants and gambling are haraam, but because they are weak in faith and are overwhelmed by whims and desires or greed for money, their belief that these things are haraam does not stop them from dealing in these forbidden things. According to the belief of Ahl al-Sunnah, they are not regarded as kaafirs because of their dealing in those things, so long as they do not believe that that is permissible.
Whoever studies or teaches manmade laws and believes that ruling by them is permissible, whether he believes that sharee’ah is superior to them or not, is a kaafir in the sense of major kufr, according to the consensus of the Muslims, because by believing that it is permissible to rule by man-made laws that go against sharee’ah he is regarding as permissible something that no Muslim has any excuse for not knowing that it is haraam. So he comes under the same ruling as one who regards adultery or alcohol etc as permissible, and because by believing these laws to be permissible he is disbelieving in Allaah and His Messenger and rejecting the Qur’aan and Sunnah. The scholars of Islam are unanimously agreed that the one who regards as permissible something that Allaah has forbidden, or regards as forbidden something that Allaah has permitted, which is well known in Islam and no Muslim has any excuse for not knowing it, is a kaafir. Whoever studies the words of the scholars of all four madhhabs on the rulings on apostates will understand what we have said clearly.