The (soon-to-be) prisoners dilemma

From the NYT, Robert Frank on fighting crime with game theory:

To see how it works, suppose that all drug violence in a city is committed by members of one of six hypothetical gangs — the Reds, Whites, Blues, Browns, Blacks and Greens — and that the authorities have enough staffing to arrest and prosecute offenders in only one gang at any one time. Mr. Kleiman proposes that the police publicly announce that their first priority henceforth will be offenders in one specific gang — say, the Reds (perhaps because its members committed the most serious crimes in the past).

This simple step quickly persuades members of that gang that further offenses will result in swift and sure punishment. And that is enough to deter them.

This works well until the gangs are made up of economists.