The high court will rule on a handful of charter challenges brought by a convicted terrorist and two accused terrorists, key among them whether Canada's post 9-11 anti-terror law violates the constitutional guarantees to freedom of expression, association and religion.
The long-awaited rulings could determine whether the terror legislation needs to be amended or rewritten, or is struck down for giving law enforcement too much latitude.
The ruling also will decide the fate of former Ottawa software engineer Momin Khawaja, the first person charged under the law, and two other men, awaiting extradition to the United States, where they face charges of supporting the banned Tamil Tigers terrorist group.
Khawaja is now serving life in prison with no chance of parole for 10 years, after the Ontario Court of Appeal took the unusual step of increasing his original 10-and-a-half year sentence to send a message about terrorism.
The high court will also rule on whether Khawaja's stiffened sentence should be upheld, and whether the extradition order approved by Justice Minister Rob Nicholson against Suresh Sriskandarajah and Piratheepan Nadarajah should be overturned.
The overarching feature of the Supreme Court ruling will focus on how terrorism is defined in the Canadian law, which came into effect two months after the 9-11 al-Qaida attacks on the United States.
Lawyers for Khawaja, Sriskandarajah and Nadarajah argued that the law's so-called motive clause constitutes a rights violation because it targets a particular thought and expression.
More broadly, they have argued that the law constitutes a charter violation that will lead to a chilling effect on certain people, discouraging them from gathering, and legitimizing religious and political profiling by the authorities.
Federal lawyers countered that the free-speech protections offered under the charter are not absolute and do not extend to protecting violence or threats of violence.
The Supreme Court will have to decide how much charter protection should be given to expressions of violence, and whether you can criminalize such conduct.
In repeated rulings, the high court has upheld the principle that a violent expression is not necessary protected under the charter's free speech guarantee.
The anti-terror law requires prosecutors to prove terrorist conduct was performed for political, religious or ideological reasons.
At Khawaja's trial, Justice Douglas Rutherford ruled that the motive provision was unconstitutional, but still ordered the trial to proceed.
The appeal court overturned Rutherford's constitutional ruling, as well as increasing Khawaja's sentence.
Khawaja was arrested in 2004 and convicted in 2008 of training at a remote camp in Pakistan, providing cash to a group of British extremists and offences related to building a remote-control detonator, known as the Hi-Fi Digimonster.
The prosecution failed to prove Khawaja knew the detonator was to be used to detonate a 600-kilogram fertilizer bomb in downtown London as part of a plot hatched by terrorists there.
Sriskandarajah and Nadarajah, meanwhile, are challenging their extradition to the U.S., where prosecutors allege they tried to purchase $1-million worth of guns and rockets for the Tigers.
The men were freed on nearly $1.2 million worth of bail two years ago after the Ontario Court of Appeal rejected their appeal.
Sriskandarajah is charged with acquiring aviation equipment, submarine and warship design software and other communications equipment for members of the Tamil Tigers. He is also charged with laundering money and counselling group members on how to smuggle goods.
Nadarajah is charged with trying to buy surface-to-air missiles and AK-47s on behalf of the Tamil Tigers from an undercover law enforcement officer posing as a black-market arms dealer.