"Not quite....if your beliefs are contradicting the law of the land, then you will punished according to the law
I'll give you a good comparison, some people believe that it's okay to have as many wives as they want (mormons) yet it's a crime in the US and is punishable"
But you said that I would not be held accountable according to Shari'a. That my scriptures, which don't exist would apply. So what do we have, Shari'a, other scriptures, and then secular law I would assume? Well, the secular law would probably not outlaw fornication.