Most countries in the world have adopted secularism to a certain extent but some, particularly in the Middle East, still retain governments that follow a particular religion's laws and enforce them on the population. This makes it almost impossible to guarantee the freedom of belief or worship of each individual and, as history has shown, religion in government invariably leads to the belittling of the rights of the dissenting sector of society.
Islam and secularism are on two opposite sides of the spectrum. One of the most fundamental and basic tenets of Islam involves surrendering oneself to God and his revelation. This includes every aspect and moment of one's life. Muslim's in a sense surrender their lives to God. This makes it completely opposite to secularism, which seeks to separate God from matters of the state. Islam is fundamentally opposed to secularism and many Islamic scholars reject secularism completely. There are two main reasons why Islam rejects secularism.
The first of the two reasons why Islam and secularism are so opposed is that secularism allows by law practices that are unlawful in the Qur'an and in God's revelation. Shari`ah, or God' law, is obligatory for Muslims and there are some very basic rules of this that are completely beyond discussion. Islamic law covers many aspects of daily life, from how to worship and pray, what he may or may not eat or drink, the relationships between men and women in Muslim society, matters of hygiene and community. It also includes many procedures and legal transactions that in a secular society are usually handled by the courts or by the government. Things such as divorce, inheritances, and business transactions all have legislation in the Qur'an that guide Muslims as to how to go about these.
There are several examples of how secularism completely contradicts Islamic law. The Qur'an is quite explicit about the illegality of adultery but secularism makes it legal as long as it is between consenting adults. Interest is also the base on which rests the economic system of almost every secular country. Interest on money, also known as Riba, is unlawful according to the Qur'an. The selling and consumption of alcohol and pork are also completely legal in secular society. According to Islamic law, the selling and consumption of alcohol are completely off limits to Muslims.
The second reason why Islam rejects secularism is that secularism represents unbelief, engaging in secularism implies that the individual in question is an unbeliever. Secularism governs with laws that are not handed down by God, it separates God from people's lives. Secularism claims that many of the laws in the Qur'an were suitable hundreds of years ago when they were revealed but now can serve no practical purpose in the modern world. By engaging in secularism there is a choice being made. The rules of man are explicitly being chosen over the rules of God. This is a complete contradiction of Islam. In the Qur'an it is explicitly stated that those that do this are seeking a judgment based on ignorance. The question is asked, if you are truly a believe in God, then what better judgment is there than that of God? The Qur'an states that anyone that fails to judge by the revelation of God is a non-believer. Secularism is by definition the acceptance of rulings other than those in the Qur'an and as such can never have a place in Muslim society. It's very concept is contrary to the basic understanding of what it means to be a believer. Islam is by definition an act of surrendering oneself to the will of Allah.
Many scholars argue that secularism has no place in Islam and should be rejected by Muslims. By taking the Western view of religion Islam is restricted to the mosque and to peoples hearts and has no place ruling a community or their lives outside of the mosque. The very basis of Islam is against personal freedom and government by the people. Islam is centered completely around the complete surrender of every aspect of an individual's life to the rule of God. Secularism is quite difficult to introduce into a Muslim society because in itself it destroys the idea of a “Muslim society.” Even so, in this age of information secularism is quickly taking hold around the World. Many corrupt governors and religious leaders have taken advantage of Islam to trample on the basic rights of the people they govern and as a consequence, Muslims all around the World have started to rebel and ask for some sort of secularism in their government, to avoid these excesses.