Current Legal Status

At present, cannabis is a controlled substance under the federal Controlled Drugs and Substances Act. This means it is illegal to possess, sell, produce, import or export cannabis anywhere in Canada, unless authorized under the Act.
 

Medical Cannabis

Under the Controlled Drugs and Substances Act, the federal Access to Cannabis for Medical Purposes Regulation (ACMPR) allows authorized individuals to grow their own cannabis for medical purposes or obtain it from a licensed commercial or designated producer. To obtain an authorization, individuals are required to obtain a recommendation from a physician, register with a licenced producer (or with Health Canada if they wish to grow cannabis for personal use or have someone grow it for them) and adhere to the possession, storage and production limits set out in the regulation.
 
Currently, the only legal commercial source of quality-controlled cannabis for medical purposes in Canada is through purchase directly from one of the 58 producers licenced by Health Canada – 14 of which are based in British Columbia (as of September 5, 2017).
 

Cannabis – What Is It?

While “marijuana” and “cannabis” are often used interchangeably, the term “cannabis” refers to products made from the cannabis plant, while the term “marijuana” refers specifically to the dried flowers and leaves of the cannabis plant.
 
The following overview of the properties of cannabis is taken directly from A Framework for the Legalization and Regulation of Cannabis in Canada, p. 68-70

The cannabis plant has been used for millennia for its psychoactive effects—euphoria (“the high”), relaxation, a sense of well-being, and intensification of ordinary sensory experiences (i.e., sight, sound, taste, smell). It has also historically been used for medical and social purposes.

Cannabis contains hundreds of chemical substances, among which are over 100 known as “cannabinoids.” These are chemical compounds that act on receptors in cells in the brain and body.

The most well-studied cannabinoid is THC (tetrahydrocannabinol), the primary psychoactive compound of cannabis (i.e., the chemical responsible for the “high”).

Another key cannabinoid is cannabidiol (CBD). Unlike THC, CBD is not psychoactive and may in fact counteract some of the psychoactive effects of THC. There is increasing scientific study into the potential therapeutic uses of CBD.

 

THC Concentration

Health Canada notes that “the potency (concentration) of THC in cannabis is often presented as a percentage of THC by the weight of a specific part of the plant. The THC potency in dried cannabis has increased from an average of 3% in the 1980s to around 15% today. Some strains can have an average of as high as 30% THC.”