In Christian & Islamic Theology, one could argue that there can't be Creation Ex Nihilo since 'before' Creation there was God.
In Philosophical Naturalism (which is not Physicalism - it subsumes it), one could have an eternally existing universe, as per Hoyles (now neglected) steady-state universe; in the Big Bang theory, one could argue that whatever physical laws hold in time there must be laws that hold outside of time that condition the creation of the universe; laws are of course not nothing.
In Buddhism, it appears that the universe is eternal (though cyclical).
In all three, Nothing, does not obtain at any time.
One is reminded here of Parmenides - non-being is not.
This points towards a supposition: Creation Ex Nihilo is impossible in the strict sense; when I say strict I mean Nothing should be taken in Parmenides sense, and not say Hegel, where it means pure indeterminiteness.
Am I justified in holding to this - or are there good counter-arguments?