In an excellent and interesting article, John Quiggin surveys the environmental issues of the Murray–Darling basin and, citing the relevant economic literature, proposes an eclectic approach to their solution. Quiggin’s preferred policy framework involves three elements: taxing the polluter; creation of new forms of communal property rights (to encourage Coasian bargaining or internalisation); and regulation (also to assist in achieving sustainability). I make three connected comments. Buchanan and Stubblebine (1962) showed that the combination of Pigovian taxation and Coasian bargaining, of the kind that Quiggin wishes to encourage, can be inconsistent in that bargaining can move the economy away from the Pareto efficient allocation that would be achievable by taxation alone. My second comment revolves around the dual meanings of the words ‘unilateral’ and ‘reciprocal’. Quiggin concentrates on externalities that are unilateral in a physical sense. In contrast, Coase (1960) assumes as a practical matter that externalities are reciprocal in an economic sense. If so, it tells against many strong claims in favour of specific forms of public intervention – Coase claimed regulating the polluter, or awarding damages against the polluter, or taxing the polluter will not necessarily improve the efficiency of the allocation of resources. My final remarks relate to the concept of efficiency used by Quiggin and Coase, and how Quiggin’s economics leads him to what I take to be the central message in Coase (1960). My comments relate only to efficiency and not directly to equity considerations; 1 nor to Quiggin’s argument concerning the value of notions of sustainability.