Worth reading in the wake of Rahm Emanuel's first budget proposal: Mick Dumke and Ben Joravsky on the high cost of marijuana arrests and prosecution. They put the tab at $78 million a year. Which is quite close to the Drug Policy Alliance's estimate that New York City spent $75 million on possession arrests and prosecution in 2010, and one in seven of all arrests were for "lowest-level" marijuana possession. Dumke and Joravsky estimate that the CPD makes 23,000 possession busts a year; in 2009, the CPD totaled 181,669 arrests in all, making Chicago's percentage about the same (a bit less than one in eight).

Chicago's arrests for pot possession haven't exploded in the way that New York City's have, but they're still up: in 1989, according to the CPD's annual report, the total number of marijuana-related arrests was 9,285. This is in line with broader national trends; according to "The War on Marijuana: The transformation of the war on drugs in the 1990s" by Ryan S. King and Marc Mauer, "marijuana arrests increased by 113% between 1990 and 2002, while overall arrests decreased by 3%." And the concern over the cost of arrests and prosecution is not new, either. King and Mauer write:

In Chicago, similar concerns have been raised, this time in a report submitted by a city police sergeant [in 2004]. Sergeant Thomas Donegan noted that the vast majority (over 90%) of marijuana arrests in Chicago were dismissed or dropped, leading him to question why law enforcement agents were dedicating significant resources to pursue marijuana when approximately nine of ten cases will not result in a conviction. Donegan recommended the use of fines rather than arrest for marijuana use, a proposal endorsed by Chicago Mayor Richard M. Daley.

Seven years later, Joravsky and Dumke found an identical percentage of arrests were tossed out in court, around the same time Garry McCarthy was suggesting exactly the same thing Donegan did—fines instead of arrest.

Why does this allocation of police resources continue? The main cause usually cited is the "broken windows" theory of law enforcement pioneered by William Bratton (a McCarthy mentor) in New York City, the principal reason New York's marijuana-possesion arrests have increased so much in the past couple decades. But this basis for the low tolerance of possession has come in for substantial criticism. In "Deterrence and Public Policy: Trade-Offs in the Allocation of Police Resources," (PDF) Bruce Benson, David Rasmussen, and Iljoong Kim address the "zero sum" nature of law enforcement and argue that the time spent on low-level drug arrests leads to increases in Index I—i.e. the most serious—crimes:

The increased law enforcement emphasis on drug arrests has significantly altered the incentives facing the crime-prone population, but not in ways that are typically suggested by drug-control advocates. Drug enforcement policy apparently has drawn resources away from Index I crime control, has caused some drug criminals to shift into nondrug crime, or both. The coefficient on DRUG-ARRj implies that allocating the resources necessary to make one more drug arrest a year results in about 0.7 more Index I crimes that year. These results, therefore, support the deterrence hypothesis: Policing does influence the incentives to commit crime.

Or, as Jens Ludwig and Bernard Harcourt write in "Reefer Madness: Broken Windows Policing and Misdemeanor Marijuana Arrests in New York City, 1989-2000" (PDF):

The positive relationship between the change in MPV arrests and serious crime, when prior crime levels are held constant, means that, controlling for mean reversion, an increase in MPV arrests over the period translates into an increase in serious crime—not, as the broken windows theory would predict, a decrease in serious crime. This result is exactly the opposite of what we would want in terms of the effect of MPV arrests. It suggests that this policing strategy focused on misdemeanor MPV arrests is having exactly the wrong effect on serious crime—increasing it, rather than decreasing it.

John Fritchey, La Shawn K. Ford, and Walter Burnett Jr. have gone so far as to gently float the idea of legalization, or at least talking about doing so. But don't get your hopes up: the tension between state and federal law remains, and if anything the Obama administration has been more aggressive about that gray area than its predecessors:

U.S. Attorney Laura Duffy of Southern California has said that she is ready to go after newspapers, radio stations and other outlets that run ads for medical marijuana shops because federal law targets those who place ads for an illegal substance. Duffy told California Watch, "I am willing to read (the law) expansively, and if a court wants to more narrowly define it, that would be up to the court."

It's actually a very recent development, as Salon's Justin Elliott points out—the momentum has actually substantially shifted at the federal level in recent months, and anything pushed at the local level will inevitably encounter the atmosphere higher up the ladder.