https://en.m.wikipedia.org/wiki/Quis_custodiet_ipsos_custode...

excerpt of the first few paragraphs, sorry about any wrong formatting, links becoming plain text, etc. just pasted it as is:

Quis custodiet ipsos custodes? is a Latin phrase found in the Satires (Satire VI, lines 347–348), a work of the 1st–2nd century Roman poet Juvenal. It may be translated as "Who will guard the guards themselves?" or "Who will watch the watchmen?".

The original context deals with the problem of ensuring marital fidelity, though the phrase is now commonly used more generally to refer to the problem of controlling the actions of persons in positions of power, an issue discussed by Plato in the Republic.[citation needed] It is not clear whether the phrase was written by Juvenal, or whether the passage in which it appears was interpolated into his works. Original context edit

The phrase, as it is normally quoted in Latin, comes from the Satires of Juvenal, the 1st–2nd century Roman satirist. Although in its modern usage the phrase has wide-reaching applications to concepts such as tyrannical governments, uncontrollably oppressive dictatorships, and police or judicial corruption and overreach, in context within Juvenal's poem it refers to the impossibility of enforcing moral behaviour on women when the enforcers (custodes) are corruptible (Satire 6, 346–348):

audio quid ueteres olim moneatis amici, "pone seram, cohibe." sed quis custodiet ipsos custodes? cauta est et ab illis incipit uxor.

I hear always the admonishment of my friends: "Bolt her in, constrain her!" But who will watch the watchmen? The wife plans ahead and begins with them!