Associated PressBOULDER — The University of Colorado is open to the public on this 4/20 marijuana holiday for the first time in three years. The university has blocked public access in recent years in an effort to snuff out crowds smoking pot to mark the unofficial celebration. But CU President Philip DiStefano said in a letter to students that the closures in recent years have successfully sent the message that 4/20 celebrations were disrupting the school's academic mission.