In this paper, I intend to argue against Alexander Bird‟s thesis (2001) that the law salt dissolves in water is metaphysically necessary. I briefly indicate Bird‟s argument for the necessity of such law, and then I provide a counter-argument to his thesis. In a general way, Bird wants to show that the existence of certain substances depends on the truth of certain laws, and that because of this the existence of such substances implies the existence of such laws. That would make the laws existing at least while the substance it rules exists; what, for Bird, makes such laws metaphysically necessary. My counter-argument to Bird is that such conception apprehends just what we call “weak necessity”, and not the strong necessity we would like a metaphysically necessary law to have.