States together spent somewhere around $3.6 billion enforcing marijuana possession laws in 2010, according to a new study by the American Civil Liberties Union, entitled "The War On Marijuana In Black and White." That's the authors' "best estimate," though approximations using different methodologies put the cost as high as $6 billion and as low as $1.2 billion.

The paper grabbed headlines Tuesday with its finding that blacks are nearly four times as likely as whites to be arrested for possessing marijuana, despite both races using the drug at about the same rate.

(Read more: Gallery of Medical Marijuana)

Here are some most startling numbers from the ACLU's report with regards to the cost of enforcing marijuana laws:

$20 billion: The amount states will spend enforcing marijuana laws over the next six years.

(Read more: The Huffington Post:

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