Res Communis, Res Nullius and Res Publicae

In one line

Roman law sorted things into five classes according to who could own them, and Indian public trust cases still argue in three of those classes.

In the wording a student can write in an exam: the Institutes of Justinian, Book II Title I, divide things into those which admit of private ownership and those which cannot belong to individuals, and of the latter some are by natural law common to all, some are public, some belong to a society or corporation, and some belong to no one; and the first class is stated as the air, running water, the sea, and consequently the seashore, from which no one is forbidden access.

The five classes

Res communes, common to all by natural law. The Institutes name the air, running water, the sea, and consequently the seashore. Nobody may be forbidden access to the seashore, provided he abstains from injury to houses, monuments and buildings, which are not, like the sea itself, subject to the law of nations. These things cannot be owned by anyone at all, not even by the State.

Res publicae, public things. All rivers and harbours are public, so that all persons have a right to fish in them. The public use of a river's banks, and of the seashore, is part of the law of nations: anyone may bring his vessel to the bank, fasten cables to the trees, and use it as a resting place for cargo; anyone may build a cottage on the shore for shelter, dry his nets and haul them from the sea. But the ownership of the bank belongs to the owner of the adjoining land, and the shore itself belongs to nobody as private property.

Res universitatis, things of a corporation. The Institutes give buildings in cities, theatres and racecourses, belonging to cities in their corporate capacity.

Res nullius, things belonging to no one. The Institutes' examples are things sacred, religious or sanctioned, which belong to no one because what is subject to divine law is nobody's property. In the later use the term also covers a thing capable of ownership which has no owner yet, the wild animal being the standard case, and it is in that second sense that the phrase reaches this paper.

Res privatae, things in private ownership, which the Institutes say most things are.

The two distinctions that matter for an answer

Res communes and res nullius are not the same. A res communis cannot be appropriated; a res nullius can, by the first taker. Air is res communis; a wild deer is res nullius until somebody takes it. A student who translates both as "belonging to nobody" has lost the distinction the module is about.