The Quran contains the law that was revealed to a man, Muhammad Ibn Abdullah, and he acted upon the words as they were revealed. This acceptance that there is only one law book for all men is called "Tawheed." Tawheed or the way of following one law for all mankind, is the constitution to follow and that constitution is nothing but the laws of the Creator revealed to man in the Quran. Of course, it is the promise of Allah that the believers will inherit the earth. This is the common law for all men at all times and all places. Man will free himself from the slavery of anything to be the slave of Allah alone and to worship only Him, to follow his direction, and to seek help from Him alone. Allah has guaranteed his unity on earth upon that law as in Sura 28, Aya 5:

"And we have bestowed our grace upon those who were being oppressed in the land, and made them the leader (in faith) and inheritors of the earth."

And Allah is the end of affairs. And the final struggle will result to the way of Allah and those who are in the path.