How to create a black market

California's ban on tobacco in prisons has produced a burgeoning black market behind bars, where a pack of smokes can fetch up to $125.

Prison officials who already have their hands full keeping drugs and weapons away from inmates now are spending time tracking down tobacco smugglers, some of them guards and other prison employees. Fights over tobacco have broken out -- at one Northern California prison guards had to use pepper spray to break up a brawl among 30 inmates.

The ban was put in place in July 2005 to improve work conditions and cut rising health care costs among inmates but it also has led to an explosive growth of tobacco trafficking. The combination of potentially big profits and relatively light penalties are driving the surge.