Beyond their issues with process, the law enforcement groups made it clear that they did not agree with the policy decision. The sky would fall if people could buy and smoke pot legally, the cops warned.
"The decision by the Department ignores the connections between marijuana use and violent crime, the potential trafficking problems that could be created across state and local boundaries as a result of legalization, and the potential economic and social costs that could be incurred," they wrote. "Communities have been crippled by drug abuse and addiction, stifling economic productivity. Specifically, marijuana's harmful effects can include episodes of depression, suicidal thoughts, attention deficit issues, and marijuana has also been documented as a gateway to other drugs of abuse."
As if that were not enough, the cops also warned of "grave unintended consequences, including a reversal of the declining crime rates" of the past decades. But they didn't explain how allowing for legal marijuana sales in Colorado and Washington would cause crime to increase.
http://www.cannabisculture.com/content/2013/09/03/Cops-Cry-Foul-Over-Holder-Marijuana-Policy-Move