Full Idea
One might have a singularist view of causation in which a cause necessitates its effect, but they need not be subsumed under a law, ..and there are identities which are metaphysically necessary without being laws of nature.
Gist of Idea
Singular causes, and identities, might be necessary without falling under a law
Source
Stephen Mumford (Laws in Nature [2004], 04.5)
Book Reference
Mumford,Stephen: 'Laws in Nature' [Routledge 2006], p.63