What you said,,, Can you clarify who enacted this law that who believes in One God is a muslim?
And strive for Allah with the striving due to Him. He has chosen you and has not placed upon you in the religion any difficulty. [It is] the religion of your father, Abraham. Allah named you "Muslims" before [in former scriptures] and in this [revelation] that the Messenger may be a witness over you and you may be witnesses over the people. So establish prayer and give zakah and hold fast to Allah . He is your protector; and excellent is the protector, and excellent is the helper. [Al-Haj: 78]