The U.S. Justice Department is attempting to solve a problem that almost no one knew about with a solution that almost no one asked for. The results -- so far, confusion and uncertainty -- have been entirely predictable.

The department announced this month that it would permit marijuana legalization on 300 or so Indian reservations in 30 states. The decision has perplexed American Indian leaders, who say that the last thing many tribes want is more lax federal law enforcement.

Whatever one may think of legalizing marijuana -- and there are plenty of causes for concern, especially regarding its health effects -- the way to do it is not to let Attorney General Eric Holder simply pick and choose which federal drug laws he will enforce. Yes, prosecutors have discretion, and it may make sense to use it when a state's voters decide to legalize pot. It makes less sense when local officials not only haven’t asked, but also rely on the federal government for law enforcement, as is the case with Indian reservations.

It's not a matter of autonomy -- tribal rights are protected by treaty -- so much as public health. American Indians have rates of alcohol dependency well above the national average. Ditto for tobacco and illegal drug use. Mortality rates, too. Keep in mind that regular marijuana use causes respiratory problems and impairments in thinking and memory (especially in young people), and that for many it leads to addiction.