Full Idea
A law of nature tells us what kinds of things, events and properties (all else being equal) go along with what. The 'must' of natural necessity has its place here because it is bound up with a model or analogy representing generative mechanisms.
Gist of Idea
Laws of nature state necessary connections of things, events and properties, based on models of mechanisms
Source
Rom Harré (Laws of Nature [1993], 5)
Book Reference
Harré,Rom: 'Laws of Nature' [Duckworth 1993], p.114
A Reaction
This is Harré's final page summary of laws. I agree with it. I would say that the laws are therefore descriptive, of the patterns of behaviour that arise when generative mechanisms meet. Maybe laws concern 'transformations'.