I think I've found it. The original is a usenet post by "Perry E. Metzger" from 1993,

https://cypherpunks.venona.com/date/1993/04/msg00559.html

https://www.clock.org/~fair/opinion/parable.html

I've found three comment threads on HN referencing it (through either of those two URL's),

https://hn.algolia.com/?query=ruritania%20police&type=commen...

Cheers!