Legalization of Marijuana through religous justification
Essentially, in order to challenge the constitutionality of legislation you have to prove that....
I. A breach of a Charter right, in this case s.2(a)--freedom of religion and conscience
Does the law which forbids possession of marijuana infringe on the Charter right on freedom of religion and conscience? Freedom of religion is a fundamental right of the Charter , meant to insulate citizens from a state religion and to allow citizens to practice whatever religion they want, no matter how absiludicrous it may seem.
You would have to prove that smoking marijuana is an element of your religion, and that is all in order to get past this stage. Even if you were the accused in a murder case and you are pleading that it's part of your religion, you would get past this stage.
II. The breach of the charter right is not saved by s.1 of the Charter--all rights are subject to reasonable limits prescribed by law as can be demonstrably justified in a free and democratic society [In this case, you would have to prove that restricting the use of marijuana in accordance with]
Here is the very difficult part. Laws which forbid the possession and trafficking of drugs are designed to prevent harm to society. The counsel for the defendant could adduce medical studies, witnesses and other evidence to demonstrate that the laws against possession of marijuana are unreasonable. [If there was a law which criminalized the possession of crosses or turbans, obviouslyhthe provision would be unreasonable because crosses are merely a religious symbol and harm nobody]. Marijuana, as much as we all love it, does have deletrious effects [loss of memory, cognitive impairment, decrease in production etc.] If you can convince the court on a balance of probabilities that criminalizing the possession of marijuana is an unreasonable infriningement on your basic fundamental right to freedom of religion [perhaps through a cost /benefit analysis] then you will likely be in very good shape.
III The impugned legislation is not connected to the objective of the legislation in a way that minimally impairs the rights and freedoms of individuals
At this stage a defendant's counsel would have to prove that the objective of preventing harm to society is not met by the current marijunana possession legislation in a way that really protects our basic, supreme rights and freedoms. The Crown will argue that the legislation meets the objective in a way that minimally infringes the rights: criminalizing the possession of marijuana is meant to deter potentially harmful behaviour and it is a very minor infringement on our freedom of religion and conscience
I'm not sure if there has been a case like this before any of the courts, but in all honesty I think it would be difficult to get through this three pronged test. There's a higher probability that the Narcotics Act will be ammended before someone is able to make a s.2(a) argument.