Given the number of states that currently permit the use of medical marijuana - and the fact that two states currently permit recreational use of marijuana- and in light of President Obama's public statements that the DEA would not prioritize pursuing persons participating in the production of medical marijuana as per state law, it believe it is just and correct to issue a federal pardon to those charged with said offense when no other federal law is violated.
I understand that the president cannot tell the DEA to simply look the other way but he can issue a pardon or blanket amnesty in light of the fact that the states have permitted this and that the punishment is excessive. It is within presidential authority to issue pardons.