This enabled them to justify taxation. [fact]
But the physiocrats straightaway added this: Economic agents must be left free, but, first, we must take account of the fact that the entire territory of a country is basically the sovereign's property, or at any rate that the sovereign is co-owner of all the land of the country and so is therefore co-producer. This enabled them to justify taxation.
Michel Foucault, The Birth of Biopolitics, loc. 1459