How can it be that after the state of New York decriminalized possession of personal use quantities of marijuana, New York City police still manage to rack up tens of thousands of marijuana arrests every year — including 33,000 arrests just in 2006?

That’s the question that the New York City Bar will address at a panel tomorrow.

The panel will also go beyond the raw numbers to ask the slightly dicier question: why is it that these arrests are overwhelmingly concentrated in black and latino neighborhoods? Should be interesting stuff!

As a side note, it should go without saying that the New York City numbers are just part of a large national problem. There were more than 800,000 marijuana arrests nationwide in 2006. These arrests are directed overwhelmingly at minority communities, despite comparable levels of drug use across ethnic groups, as was documented in considerable detail in a report released last year by the Justice Policy Institute.

What makes New York particularly interesting is that this type of pattern is still happening despite the fact that the law was changed, ostensibly to permit possession of small quantities of marijuana. If there was ever a clear example of the dramatic impact that policing choices can have on drug policy, New York City would seem to be it.