They'll likely try one day anyway.
The method to stop them is quite simple:
1. Identify the favored classes of the regime, those you know expect and demand protection.
2. Target those classes.
3. Regime is forced to disperse protective forces outside their own "protective envelope".
4. Target those forces outside the protective envelope.
Bracken: What I Saw At The Coup
http://westernrifleshooters.wordpress.com/2012/09/11/what-i-saw-at-the-coup/