I was convicted in August 2011 of a disorderly persons charge(marijuana poss. Under 50 grams)and since I didn't have a criminal record, I was given the "conditional discharge" of 12 months unsupervised probation. I would like to visit Canada, either the end of this year or Jan or Feb. 2012... Am I prohibited from crossing the border till my probation is over in August? Or can I still visit while I'm on the probation?

I'm ex-US Customs. What are the terms of your probation? Are you allowed to leave the Province/Country?

I say if you are stopped you will not be allowed to enter. At this point your sentence is considered to be "pending" in the eyes of the US authorities.