The top court on Friday also rejected the appeals of two men seeking to avoid extradition to the United States, where they are wanted on charges related to terrorism.
The top court justices ruled that violent acts are not protected under the Charter of Rights and Freedoms.
The key issue in the appeals of Khawaja, and the two men seeking to avoid extradition, centred on the Anti-terrorism Act's motive clause, which states that terrorist activity is committed "in whole or in part for a political, religious or ideological purpose, objective or cause."
The three men argued the law has the effect of "chilling the exercise of freedom of expression, freedom of religion and freedom of association; and …it would legitimize law enforcement action aimed at scrutinizing individuals based on their religious, political or ideological beliefs."
Court dismisses complainants' argument
However, in its 7-0 decision written by Chief Justice Beverley McLachlin, the Supreme Court said the purpose of the law does not infringe on freedom of expression.
"While the activities targeted by the terrorism section of the Criminal Code are in a sense expressive activities, most of the conduct caught by the provisions concerns acts or threats of violence," the court said.
In the Khawaja case, the top court judges also considered whether a sub-clause in the law exempting terrorist activity "committed during an armed conflict" applied in his case. The court rejected Khawaja's assertion that his activity fell under that exemption.
"The purpose of the armed conflict exception is to exempt conduct taken during an armed conflict in accordance with applicable international law," the court said. "There is no evidential foundation for the application of this exception in the present case: the conduct cannot be said to have been taken solely in support of an armed conflict, nor was it in accordance with applicable international law."
Arrested in 2004, Khawaja, a Canadian-born computer programmer, was convicted in 2008 of financing and facilitating terrorism, and building a remote-control device that could trigger bombs.
His initial sentence of 10½ years in prison was increased in December 2010 by the Ontario Court of Appeal to life imprisonment with no chance of parole for 10 years.
On Friday, the Supreme Court upheld the lengthier sentence imposed on Khawaja by the appeal court.
Lawrence Greenspon, who represents Khawaja, said he was "not happy with the result" of his client's court challenge.
"I have faith in the courts that they can distinguish between who is innocent and who is not," Greenspon told reporters outside the court in Ottawa after the ruling. "I don't think we can say with equal confidence that investigations and prosecutions will not involve and will not be based on political, religious or ideological beliefs in this country."
Justice minister pleased with court decision
In the cases of Suresh Sriskandarajah and Piratheepan Nadarajah, the Supreme Court said they can be sent to the U.S. to face charges of supporting the Tamil Tigers, a Sri Lankan rebel group on Canada's official list of terrorist organizations.
Sriskandarajah, former president of the Tamil Students Association at the University of Waterloo, in Ontario, is alleged to have laundered money and conspired to procure and smuggle equipment for the Tigers. U.S. prosecutors charged Nadarajah with attempting to buy missiles and AK-47 assault rifles on the Tigers' behalf.
Canada's anti-terrorism law came into effect a few months after the Sept. 11, 2001, attacks on the United States.
Justice Minister Rob Nicholson said he was pleased that the court upheld the constitutionality of the key provisions in the anti-terrorism act.
"By upholding this sentence, the court sent a strong message that terrorism will not be treated leniently in Canada," he said in a statement.
"I am also pleased that the court has recognized that the principles of procedural fairness were appropriately respected in the extradition cases of Mssrs. Sriskandarajah and Nadarajah, and that their surrender for extradition was justified."Suggest a correction