I hope that fear of the law would deter them from doing anything stupid, although Muzslime can easily be psychotic enough not to give a damn about the consequences. Why should they be? Opinion polls show most Americans believe that hardcore terrorists have been "mistreated" in custody.
Let's hope that they decide that by allowing their daughter to live, they will show a "humane" face of Islam in order to do taqqiyah. (Not that that is a good thing, but it's a good thing for Rifqa not to be killed, of course.)