ISIS is not doing anything the Saudi regime isn&#x27;t doing in terms of oppression.  They are rivals, thus the declaration.  If ISIS claim of caliphate is legitimate under Islamic law, then the Saudi regime isn&#x27;t (or any other Muslim regime for that matter).  Furthermore, ISIS ideologues have spoken openly about the fact that the Saudi regime implements only one side of Sharia, the punitive side, leaving the mandatory social benefits aside (the state under Sharia is under obligation to provide shelter, food, and clothing for all).  It&#x27;s one way ISIS strongly appeals to Muslims under Salafi influence.