Though it refers to regulatory legalization, as is happening in Colorado and Washington, the memo indicates that the guidance is for "all states." It additionally includes "civil enforcement," which would seem to go beyond criminal prosecutions and investigations to include problems like forfeiture threats directed at landlords and so forth. As a DOJ memo it would not constrain IRS audits of dispensaries.
There is plenty of wriggle room for prosecutors to target people, if that's what Cole and Holder and Obama intend. But at a first glance at least, it looks to me like the memo is seeking to allow Colorado and Washington to proceed with marijuana legalization, and that it may help ease things up in the medical marijuana states as well.
Phil will be posting a Chronicle story momentarily.