Should the gangs during US prohibition of Alcohol been pardoned after prohibition was lifted?
Of course not. You're participating in criminal activity.
If you parked somewhere and it was a no parking zone, and then later it was changed to a legal parking spot, should you get a refund on your ticket? Of course not.
You broke the law as it stood.
If you illegally claimed a deduction on taxes one year and got thrown in jail, and then the next year it was a legal deduction, should you be released form jail? Of course not. You still committed tax evasion.
If Alcohol and Tobacco are legal, it makes no sense to ban marijuana. All the reasons for banning marijuana can easily be applied to Tobacco or Alcohol.