Yesterday one of the best marijuana decriminalization laws in the country took effect in Washington D.C. This may leave some asking why Initiative 71, the marijuana legalization measure set to make the November ballot in the District, is still necessary. Unfortunately, history has shown merely decriminalizing marijuana isn’t enough.

Decriminalization doesn’t always stop small marijuana arrests.

While the point of marijuana decriminalization is to stop people from being arrested and getting a criminal record simply for having a small amount of marijuana, in practice it hasn’t always lived up to this modest goal. The best example of its failure is New York City.

Marijuana possession has been decriminalized for decades in New York state, yet New York City arrests a huge number of people for marijuana thanks to stop-and-frisk. Using clever and/or legally questionable tactics police can still find ways to target people with small amounts of marijuana. The New York City Police Department exploits a loophole in the local law which still classifies marijuana in “public view” as a misdemeanor. They ask people to empty their pockets, which puts their marijuana in public view, so they can be arrested on this more significant charge.

Many of the other problems created by marijuana prohibition still remain.

Even if the decriminalization works as intended to stop small arrests, it does nothing to end many of the other problems created by prohibition. Without a way for people to legally buy or grow their own marijuana, it remains in the black market. Criminals continue to be enriched and often need to commit other crimes like tax evasion and money laundering to cover up their behavior. The black market also inherently makes transactions more dangerous by denying everyone a legal way to address disputes. In addition, people continue get a product of unknown quality which has not gone through safety inspections.

Only legalization can undermine the black market. Decriminalization is a positive step forward, but more needs to be done.

Jon Walker is the author of After Legalization: Understanding the future of marijuana policy

Photo by Just Say Now under Creative Commons license