"Who will guard the guards themselves?"/"Who watches the watchers?"
The string is backwards. Reverse it to get "Jnbl vnlmhwbxm bilhl vnlmhwxl"
Perform Rot7 on the string (A->H, B->I, etc.) to get "Quis custodiet ipsos custodes". (Note: I found this by doing Rot1 seven times.)
"Quis custodiet ipsos custodes" is Latin for "Who will guard the guards themselves?" The phrase comes from Juvenal's Satires.
Explanation of title:
The title is a quote from one of Juvenal's other satires.
What I thought of the puzzle:
It was fun, but fairly obvious - the last letter made step 1 obvious, and the encryption used in step 2 is fairly weak. If the string is more than just a word or two, the frequency and distribution of letters still looks like normal words (just not actual words), strongly suggesting to check that specific form of encryption.