We should be thankful to California for showing the rest of the states how not to handle medical marijuana.

Federal prosecutors announced last week an aggressive crackdown against California “clinics,” which reportedly have been operating as storefront drug dealers and using the humanitarian law as a screen for criminal operations.

California’s lax law and lazy enforcement have allowed the dispensaries to become a source of marijuana that is sold elsewhere, said U.S. Attorney Benjamin Wagner.

“California’s marijuana industry supplies the nation,” Wagner said. “Huge amounts of marijuana grown here in the state are flowing east to other states, and huge amounts of money are flowing back in the opposite direction.”

Maine, which is just establishing its medical marijuana dispensary system, should take a lesson from California about how things can go wrong.

Maine is not facing a federal crackdown because, so far, the marijuana intended for people with certain illnesses does not appear to be getting diverted to illegal uses. But if that starts to happen, the people who grow and distribute medical marijuana should be prepared to face federal law enforcement.

The issue is not whether pot should be legal for recreational use. If people want to change the law, they have the ability to make their case.

In fact, California voters rejected a proposed law in 2010 that would have legalized marijuana. What growers and dealers there are doing now is trying to use the medical marijuana system to accomplish what they failed to do at the ballot box.

This should be a warning for people involved in medical marijuana here, both in government and outside it. The potential for abuse exists, and the consequences could include the interruption of marijuana meant for patients who Maine voters have twice said should be allowed to use it.

Medical marijuana requires a complicated balancing act for states: While the medical establishment – for the most part – rejects marijuana as a therapy, a number of very sick patients and the people who care for them swear that it helps. And the disconnect between state and federal law, which considers selling marijuana, even for medicinal use, to be a criminal offense, adds a level of uncertainty.

The best thing state officials and private individuals who care about the success of medical marijuana in Maine can do is to keep federal law enforcement on the sidelines by making sure that the system runs as designed, and drugs are not diverted into the black market.