Replying to Getting into Canada

This may be a long shot on here but I'll see if any of you have been in this situation...  I'm taking a trip to Nelson/Revy/Golden next month w/some friends.  We're coming from the U.S.  One of the friends has a refusal of breathalyzer charge (which is a civil offense in Rhode Island) and a midemeanor possession of weed charge from 2006 and 2007.  We've done some research and have been in touch w/ customs and it looks 50/50 on whether the border agents will let him in.  Has anyone ever had problems getting in Canada w/these types of charges?  Just wondering if anyone has any experiences or any advice.  Thanks in advance!