This does not mean the federal government will entirely back off from enforcing drug laws, nor should it. There is a difference between marijuana and heroin, for example.
But there must be a clear federal interest. The Justice Department memo cites several such interests, including preventing distribution of marijuana to minors and to states that have not legalized the drug. The department did not foreclose federal intervention if states do not aggressively enforce local laws to protect those interests.
The Justice Department memo drew sharp rebukes from predictable sources, including state and local law-enforcement and advocates of tough enforcement of drug laws. Otherwise the news was mostly greeted with a yawn.
This is evidence that the nation, if not totally convinced on drug legalization, is ready for an end to the war on drugs. This misdirected war has come at a huge cost to law enforcement, courts and prisons, not to mention people and families unnecessarily ensnared in the criminal justice system.
A growing consensus is that drug abuse should be seen as a treatment issue, not strictly as a crime. Certainly not a crime that requires the resources of the federal government, as the Obama administration policy rightly makes clear.