Applying laws which are not mentioned in the Qur’aan or Sunnah
Question

Does applying every law that is not mentioned in the Qur’aan or Sunnah constitute kufr?
Praise be to Allah.Shaykh al-Shanqeeti said: 
It should be noted that we must differentiate between man-made systems the implementation of which implies disbelief (kufr) in the Creator of the heavens and the earth, and systems which do not imply that. This may be explained by describing systems as being of two types, administrative and legislative. With regard to administrative systems which are aimed at organizing things and making them run smoothly in a manner that does not go against sharee’ah, there is nothing wrong with this and no one among the Sahaabah or those who came after them objected to it. ‘Umar (may Allaah be pleased with him) did many things of that nature that were not done at the time of the Messenger (peace and blessings of Allaah be upon him), such as writing down the names of the soldiers in a register to keep track of who was present and who was absent, even though the Prophet (peace and blessings of Allaah be upon him) did not do that and he had not known that Ka’b ibn Maalik was not present during the campaign of Tabook until after he had reached Tabook. Similarly, ‘Umar (may Allaah be pleased with him) bought the house of Safwaan ibn Umayyah in Makkah and turned it into a prison, even though neither the Prophet (peace and blessings of Allaah be upon him) nor Abu Bakr had established a prison. Such administrative matters which are intended to make things run smoothly and which do not go against sharee’ah – such as organizing employees’ affairs and organizing work matters in a manner that does not go against sharee’ah – is a kind of man-made system that is o.k. and does not go against the basic principles of sharee’ah which aims to take care of the public interest. 
But in the case of legislative systems which go against the laws of the Creator of the heavens and the earth, referring to them for judgement constitutes disbelief (kufr) in the Creator of the heavens and the earth, such as claiming that giving males precedence over  females in matters of inheritance is not fair and that they should be given equal shares, or claiming that plural marriage is a form of oppression, or that divorce is unjust towards women, or that stoning and cutting off hands etc. are barbaric actions that cannot justifiably be done to anyone, and so on. 
So implementing this kind of system to govern people’s lives, wealth, honour, lineage, minds and religion constitutes disbelief in the Creator of the heavens and the earth, and rebellion against the divine system which was set up by the One Who created all of mankind and Who knows best what is in its interests. Glorified and exalted be He far above having any other legislator alongside Him. 
“Or have they partners with Allaah (false gods) who have instituted for them a religion which Allaah has not ordained? And had it not been for a decisive Word (gone forth already), the matter would have been judged between them. And verily, for the Zaalimoon (polytheists and wrongdoers) there is a painful torment”
[al-Shooraa 42:21 – interpretation of the meaning]
“Say (O Muhammad, to these polytheists): ‘Tell me, what provision Allaah has sent down to you! And you have made of it lawful and unlawful.’ Say (O Muhammad): ‘Has Allaah permitted you (to do so), or do you invent a lie against Allaah?’”
[Yoonus 10:59 – interpretation of the meaning]