Pardon all non-violent drug offenders.
Laws should be tested by the Libertarian Principle:
"People should be free to do whatever they want, except to initiate force, the threat of force, or fraud against other people or their property."
Drug laws violate the Libertarian Principle.
Drug laws should be repealed.
The President may need Congress to repeal drug laws, but the President can undo some of the damage done by these laws, now, by pardoning anyone charged or convicted of using, growing, or selling drugs, provided that the offender hasn't also done fraud or violence to others.