In a park in Montreal's north end, a few dozen of the hundreds of demonstrators taped their mouths shut in protest of the bill, which opponents say would allow the government to stifle protest and dissent. As they marched toward the office of Liberal leader Justin Trudeau, many of the large contingent waved signs bearing messages such as "Stop Harper," and "Activism is not a crime."
The Conservative government introduced the legislation, known as Bill C-51, in January.
The wide-ranging bill would give police much broader powers and allow them to detain terror suspects and give new powers to Canada's spy agency.
The organizers of the nationwide protest say the bill would infringe upon Canadians' civil liberties and right to privacy, especially online.
Groups such as Amnesty international have also argued that the bill’s powers to limit “threats to the security of Canada” are too broad and may allow the government to shut down legitimate dissenters and protest groups who do not go through official channels.
In Ottawa, hundreds of chanting protesters clogged the street outside Prime Minister Stephen Harper's office. They then marched onto the grounds of Parliament Hill. A protest in Edmonton similarly drew hundreds of angry marchers.
In Vancouver, a crowd of about 700 to 800 people according to a police estimate gathered in front of the city's art gallery. Aboriginal leaders and civil liberties groups spoke to the crowd through a megaphone, while onlookers cheered and waved signs.
Protester Larry Johnny said he feared that First Nations protesting mines in the province could be labelled "terrorists" for speaking out if the bill is passed.
"These rights affect me today, but they're also going to affect my grandnephews and nieces," he said. "I'm here for them, because they're the ones that are going to be growing up with these bills."
In Antigonish, N.S., protesters marched past the constituency office of federal justice minister Peter MacKay. Other rallies targeted the offices of Labour minister Kellie Leitch and Industry minister James Moore.
In Montreal, the demonstrators were joined by New Democratic party leader Thomas Mulcair, who climbed onto a milk crate and reiterated his intention to vote against the bill.
"C-51 is a bill that could seriously endanger our right to protest peacefully, to stand up against a government or an infrastructure or an economic policy," he said. "Mr Harper has never been able to give a single example of why this bill is necessary."
Protesters in Montreal also directed criticism at Trudeau, shouting "Harper terrorist, Trudeau complicit," as they marched toward the Liberal leader's constituency office. Trudeau has said that his party will support Bill-C51.
The Conservative government has said that the bill will make Canadians safer and give police and security forces the tools they need to meet terrorist threats.
But many of Saturday's protesters remained unconvinced by the government's assurances that the bill would not infringe upon Canadians' civil liberties and right to protest.
"I'm really worried about democracy, this country is going in a really bad direction," said Toronto protester Stuart Basden.
"Freedom to speak out against the government is probably at jeopardy ... Even if you're just posting stuff online you could be targeted, so it's a really terrifying bill."
Protest organizers say there were 70 events that took place across the country.
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