It is Not Permissible for Anyone to reject the Laws which Allaah has imposed upon His Creatures

Question:

There is a man who says that some of the Islamic laws need to be revised and that they need to be changed as they are not suitable for these times, such as the laws of inheritance, which grant two shares to the male. What is the Islamic ruling on those who say such things?

Answer:

The laws which Allaah has ordained for His creatures and which He has explained in His Book, or in the words of His truthful Messenger - may the best of peace and blessing from his Lord be upon him - such as the laws of inheritance, the five prayers, Zakah, fasting and such like, which Allaah has elucidated for His creatures and upon which the whole community (of Muslim scholars) agree may not be rejected by anyone, nor may they be altered, for they are laws established for the whole community in the time of the Prophet (sallallaahu alaihi wa sallam) and afterwards until such time as the Hour is established. This includes favouring the male children and their sons, the brothers of the parents, and of the father (by two shares), Because Allaah, the Most Glorified, the Most High has made it clear in His Noble Book and the Muslim scholars are in complete agreement over it. Therefore it is incumbent to do it, with faith and belief. And whoever claims that something else is better is a disbeliever, as is the one who claims that it is permissible to act in defiance to it, because he has rejected Allaah and His Messenger (sallallaahu alaihi wa sallam) and the consensus of the scholars, and it is a duty of those placed in authority to order him to turn to Allaah in repentance if he is a Muslim; he either does so or he should be killed as a disbelieving apostate from Islam. The Prophet (sallallaahu alaihi wa sallam) said:
Whoever changes his religion, kill him. We ask Allaah to protect us and all of the Muslims from trials and disobedience to the pure Islamic law.

Source:
Shaykh `Abdul-`Azeez Bin Baz
Fatawa Islamiyah Vol.1 Page 217