According to News Reports, Recreational Marijuana will be legal in Canada as of October 17th but things could get tricky going from Canada back into 'The States'.

Customs & Border Patrol Chief Officer Aaron Bowker said this, regarding dealing with Border Patrol (according to News Reports):

...it is wise to remember that the smallest amount of cannabis in your vehicle will be picked up by the K9. You could be fined $500 and if you have 25 grams or more, state law enforcement agencies will be called and you could be arrested.

And this...

 "a smell is obviously going to alert an officer and probably going to get you a secondary exam because we want to make sure the actual marijuana isn't in the vehicle."

The Legal age to use marijuana in Ontario, CA will be 18 according to News Reports.  However, Chief Officer Aaron Bowker said this:

"If you are driving over there and you do use it, either spend the night, don't drive impaired or have a designated driver just like you would if you're consuming alcohol,"

WATCH:

Here's an Eye-Opening Lecture addressing 'Surprising truths about legalizing cannabis: