Currently, only people who are authorized to have and use medical cannabis are permitted to purchase and consum Cannabis (Pot, Marijuana). These authorized individuals are subject to the same rules as tobacco smoking and electronic cigarette use.
In April 2017, the Canadian federal government introduced legislation to legalize and regulate recreational cannabis in Canada by July 2018. If passed, the proposed federal Cannabis Act would create rules for producing, possessing and selling cannabis across Canada.
Regardless, of new regulations travellers entering Canada would still be subject to inspections for prohibited goods, including cannabis.
See details here for more information.