The ruling concerned appeals by Momin Khawaja, the first person charged under Canada's Anti-terrorism Act, and by two men trying to avoid being sent to the United States to face terrorism charges.
The defendants had contested language in the Anti-terrorism Act that defined terrorism as activities "in whole or in part for a political, religious or ideological purpose, objective or cause."
They contended 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."
However, in explaining the high court's dismissal of the appeals on a 7-0 vote, Chief Justice Beverley McLachlin wrote the purpose of the law doesn't infringe on freedom of expression, the Canadian Broadcasting Corp. reported.
"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.
Khawaja, a Canadian-born computer programmer arrested in 2004, was convicted four years later of financing and facilitating terrorism and was sentenced to life in prison.
The court said Suresh Sriskandarajah and Piratheepan Nadarajah could be sent to the United States to face charges of supporting the Tamil Tigers, a Sri Lankan rebel group labeled as a terrorist entity.