As the legions of Rome conquered countries, they co-opted local men into the army. The normal Roman trooper was worried about where the loyalty of these co-opted troopers lay, especially when they were on guard duty, and developed the saying
Quis Custiet ipso custidies? (Who will Guard the Guards.)
Hence; Who will police the police? - Who will watch the watchers? Etc.
With the validators it has got to be - The Regulators!!!