Res extra commercium is a doctrine originating in Roman law

Roman law

Roman law is the legal system of ancient Rome, and the legal developments which occurred before the 7th century AD — when the Roman–Byzantine state adopted Greek as the language of government. The development of Roman law comprises more than a thousand years of jurisprudence — from the Twelve...

, holding that certain things may not be the object of private rights, and are therefore insusceptible to being trade

Trade

Trade is the transfer of ownership of goods and services from one person or entity to another. Trade is sometimes loosely called commerce or financial transaction or barter. A network that allows trade is called a market. The original form of trade was barter, the direct exchange of goods and...

d.

In some contexts, it can refer to areas beyond national borders, such as space and the seabed; "these regions are subject to a common freedom of exploitation without exercising national sovereignty."

If one conceives of a world community made up "of sovereign, territorial states ... [the implication is] that the space between these states is res extra commercium, a space that, because of its position and function within this community, is disassociated from the full package of rights to possession, exclusion, and alienation that normally may be claimed by holders of property."