A third and final ground on which a resource may be left outside the threshold of property arises in cases of moral non-excludability. Here the term "moral" refers more relevantly to matters of public morality than of private morality. That is to say that the test of moral excludability is much more closely concerned with those social conventions or mores which promote integrative social existence than with any normative judgment about individual human conduct.

The notion of moral non-excludability derives from the fact that there are certain resources which are simply perceived to be so central or intrinsic to constructive human coexistence that it would be severely anti-social that these resources should be removed from the commons. To propertise resources of such social vitality is contra bons mores:  the resources in question are nonexcludable because it is widely recognised that undesirable or intolerable consequences would flow from allowing any one person or group of persons to control access to the benefits which they confer. Following such appropriation, there would not, in Locke's well known phrase, be "enough, and as good left in common for others". Consequently the courts, by differentiating between excludable and non-excludable resources, engage constantly in a range of latent policy decisions which shape the contours of the property concept. In setting the moral limits of "property", the courts effectively recognise that there is some serial ranking of legally protected values and interests: claims of "property" may sometimes be overridden by the need to attain or further more highly rated social goals. As we shall see, it is no accident that the goals to which "property" defers often relate to fundamental human freedoms. It is in the definition of moral non-excludables that the law of property most closely approaches the law of human rights.