When a country is overwhelmingly Christian, it will never be made illegal.
Maybe Iran will make Islam illegal.
You seem unaware of the massive sociopolitical changes over the last 30 years.
An outright ban is entirely possible, just takes progressive steps - like this: http://m.townhall.com/columnists/charlottehays/2014/07/18/schumer-you-dont-have-to-convert-but-you-might-not-be-able-to-do-business-either-n1863492?utm_source=dlvr.it&utm_medium=facebook