The conquest theory applies, for example, to the invasion of the Roman provinces by barbarian tribes who divided the country and developed the feudal system based on land tenure.

But it hardly applies to present-day happenings, and at its best it cannot, to modern minds, "justify" present property rights.
The labor theory, meeting some queries where others fail, is that ownership is based on the act of production.

It is declared that every man has a right to that to which his brain and his muscle have imparted value.

It is evident that this test leaves without explanation or justification a great number of things that do exist and have existed as property.

Usually the basis of the labor theory of property is declared to be each individual's natural right to the results of his own labor, which claim is assumed to be an ultimate, undebatable, axiomatic fact.