Pillet, A. Keywords: Vested interests | Mots clefs: Droits acquis | ABSTRACT Antoine Pillet shows in his study of the General Theory of Acquired Rights that the principle of the international effect of acquired rights is much more important than expected by one, and that in fact it constitutes one of the great contributors of the whole science. After an introduction to the international recognition of regularly acquired rights, the author asks the definition of a regularly acquired right and then examines t…