Full Idea
Metaphysical necessity derives from distinguishing things which can happen and things which can't, in virtue of their nature, which we discover empirically: the metaphysically possible, I claim, is constrained by the laws of nature.
Gist of Idea
Metaphysical possibility is discovered empirically, and is contrained by nature
Source
Dorothy Edgington (Two Kinds of Possibility [2004], §I)
A Reaction
She claims that Kripke is sympathetic to this. Personally I like the idea that natural necessity is metaphysically necessary (see 'Scientific Essentialism'), but the other way round comes as a bit of a surprise. I will think about it.