For example, if Physical Laws 2.0 appears to allow me to murder someone, it must be that the FAI predicted that I wouldn't murder anyone, and if I did decide to murder someone, the likely logical consequence of that decision is that the FAI would have picked a different set of Physical Laws 2.0.

It just means that you were mistaken and PL2.0 doesn't actually allow you to murder. It's physically (rather, magically, since laws are no longer simple) impossible. This event has been prohibited.