The ‘Ulamā have clarified this, and the closest thing is the tafsīr of Ibn Kathīr rahimahullāh wherein it is stated that the one who rules by other than what Allāh has revealed then when he views that as being better than the Book of Allāh, or that his rule is better than the rule of Allāh, or that ruling by other than what Allāh has revealed is the same as the rule of Allāh or that he has a choice to rule by what Allāh has revealed or not — based on choice, then such an individual is judged with kufr. There is no doubt that such an individual is a disbeliever according to the ijmā’.
As for the individual who believes that the rule of Allah is the truth and that the men-made law (qānūn) is bāttil but he rules by it due to desire (hawā) or due to a temptation (ttam’an) that has overcome him, then such an individual is sinful and a transgressor (dhālim wa fāsiq) – yet is not judged with kufr. This is because he believes that the rule of Allāh is obligatory and ruling by other than it is bāttil (falsehood) but he has done it in order to obtain a career or due to a temptation. In this instance his ‘Aqīdah remains, as he still has his belief in the Book of Allāh and that it is the truth and has to be ruled by, then in this case his ‘Aqīdah remains. Such an individual is judged to be sinful and not judged with having kufr, because this is kufr ‘amalī (kufr of actions [in contrast to the disbelieve of the heart]).