Plato’s Dual Morality

In the first volume of  Contra Mundum (1955) one of the authors refers to the dual morality of Plato who wrote in The Republic, Book III:

Then if anyone at all is to have the privilege of lying, the rulers of the State should be the persons; and they, in else should meddle with anything of the kind. . .their dealings either with enemies or their own citizens, may be allowed to lie for the public good. But nobody else should meddle with anything of the kind. . .

It looks like the modern state has mastered Plato.