[Smirnoff]

I have a feeling you mean drug lords or cartel or drug dealers when you say narc. However, narc is actually a good guy, ie a cop or federal agent enforcing the drug laws.

[jasonwatkinspdx]

In Mexico it's common to refer to people connected to the cartels as 'los narcos'. A bit backwards from what you'd expect in English, but that's how things go when languages collide.

[theorique]

It's short for "narcotraficante" - drug trafficker. Hence, "el narco" is the drug producer/dealer.

[checoivan]

You're right, My bad. I was thinking of narc as "Narco", the drug lords.