Killing politicians and policemen in the long term is career suicide. Mexico for instance is going through a certain phase right now and while cartels will always remain - which is always the case when a noteworthy criminal phenomenon takes root - at one point a huge clamp down will happen and it will stabilize.
Cartels in Colombia used to kill judges, but eventually law enforcement came down on them hard. Nowadays Colombian cartels are still highly active, but it has become more of an underground affair.
It's amazing if you see how many powerful politicians in Colombia are tied to the cocaine business. Also the civil war is pretty much over but not the FARC's continued control over several hundred thousand coca growers in southern Colombia.
