I see nothing in the story that implies the BHO administration is supportive of states' rights.
I do, however, see an intent to placate a support base for the BHO campaign: pot users or supporters.
Pot users or supporters = hippies + libertarians + anarchists (who are closer to closet communists) + states rights supporters. A very eclectic support base for legalized marijuana that tends to lean mostly democratic, tempered by the libertarian (whose votes are arguably wasted on 5% or lesser candidates) and states rights supporters.
The Obama administration has no demonstrated respect for states' rights at this point.
The memo, the officials said, emphasizes that prosecutors have wide discretion in choosing which cases to pursue, and says it is not a good use of federal manpower to prosecute those who are without a doubt in compliance with state law.
Use of manpower is the argument. Not legitimacy of law or 10th amendment principles or other legal opinion. Just a function of available resources.