Exceptio rei venditae et traditae

An exception or plea of the sale and delivery of the thing. This exception presumes that there was a valid sale and a proper tradition; but though, in consequence of the rule that no one can transfer to another a greater right than he himself has, no property was transferred, yet because of some particular circumstance the real owner is estopped from contesting it.

Mackeld. Rom. Law, § 299.