What do you say about a Muslim community that applied the Islamic prescriptions for about one year or more and then replaced them with positive Western laws?
A: Indeed, it is obligatory on all Muslim rulers to apply Allah's Shari`ah (Islamic law) among Muslims.
They are required to do this at all times, call others to it, and impose the prescribed punishments on members of the society. Addressing His Prophet (peace be upon him), Allah (may He be exalted) says:
And so judge (you O Muhammad ﺻﻠﻰ ﺍﷲ ﻋﻠﻴﻪ ﻭﺳﻠﻢ) among them by what Allâh has revealed
But no, by your Lord, they can have no Faith, until they make you (O Muhammad ﺻﻠﻰ ﺍﷲ ﻋﻠﻴﻪ ﻭﺳﻠﻢ) judge in all disputes between them, and find in themselves no resistance against your decisions, and accept (them) with full submission.
Do they then seek the judgement of (the days of) Ignorance? And who is better in judgement than Allâh for a people who have firm Faith.
And whosoever does not judge by what Allâh has revealed, such are the Kâfirûn (i.e. disbelievers of a lesser degree as they do not act on Allâh's Laws). And whosoever does not judge by that which Allâh has revealed, such are the Zâlimûn (polytheists and wrongdoers of a lesser degree). And whosoever does not judge by what Allâh has revealed (then) such (people) are the Fâsiqûn [the rebellious i.e. disobedient (of a lesser degree) to Allâh].
Muslim rulers should observe these noble verses and adhere to the rulings by themselves (i.e. Muslim rulers) and enforce them among their peoples. If they do so, Allah will consolidate and honor them, grant them victory over the enemies, bless them with His Support and bestow on them a blessed end of life and happiness in the worldly life and in the Hereafter. Allah (Exalted be He) says:
O you who believe! If you help (in the cause of) Allâh, He will help you, and make your foothold firm.
Verily, Allâh will help those who help His (Cause). Truly, Allâh is AllStrong, AllMighty. Those (Muslim rulers) who, if We give them power in the land, (they) enjoin IqamatasSalât [i.e. to perform the five compulsory congregational Salât (prayers) (the males in mosques)], to pay the Zakât and they enjoin AlMa'rûf (i.e. Islâmic Monotheism and all that Islâm orders one to do), and forbid AlMunkar (i.e. disbelief, polytheism and all that Islâm has forbidden) [i.e. they make the Qur'ân as the law of their country in all the spheres of life]. And with Allâh rests the end of (all) matters (of creatures).
Allâh has promised those among you who believe and do righteous good deeds, that He will certainly grant them succession to (the present rulers) in the land, as He granted it to those before them, and that He will grant them the authority to practise their religion which He has chosen for them (i.e. Islâm). And He will surely give them in exchange a safe security after their fear (provided) they (believers) worship Me and do not associate anything (in worship) with Me.
No doubt, making Allah's Shari`ah the ruler on the affairs of people is a sign of victory of Islam, a way of enjoining what is good and forbidding what is evil and a righteous deed. Allah (glory be to Him) promised those who do these things to give them succession in the earth, grant them the authority to practice their religion, and give them security after having fear. We ask Allah (Exalted be He) to help the Muslim rulers to adhere to His Shari`ah, be satisfied with it, and shun anything that runs counter to it for He is the One who is Able to do so.