Let's keep this simple, no where in the Constitution does the federal government have the right to control what a citizen puts into their body.
This is a moral issue that is best left to the state and local governments to control.
If said consumption infringes on the rights of another citizen that is a different issue and should be dealt
with, DUI's for example.
It is unconscionable that citizens of this country cannot seek and be relieved of intolerable pain in their life, keeping them from being productive citizens taking away their "rights to life, liberty, and the pursuit of happiness" because Doctor's are afraid to give them pain medication because the DEA has told them they will be prosecuted as "Drug Dealers".