It isn't arbitrary, it needs no explanation, there are no loopholes, it says what it says. 

 In most cases, sure. But just like physical laws, natural law can have gray areas requiring specialists. I agree that this doesn't make it arbitrary. 

 The only thing missing from it is fraud. 

 Which is still a form of theft... 

 I assume fraud would fall under theft. 

 Yes, it should be specified though to avoid confusion, e.g. by force or fraud. 

 A unanimous jury is one possibility. 

 Who defines the law? The word „natural“  implies that we have an inherent knowledge or feeling about what is right and wrong? correct?y question is still standing where is it coming from?