All rules have exceptions, including this one.

This is a paradox of the same kind od Russell's paradox or the paradox of the barber - We already found an example with "Hofstader?? law".

In a a village , there is just one barber . The barber is the one who shaves all men that (which?) do not shave themselves.
Question: Who shaves the barber?

Ciao
Emanuela