Note: This story has been updated with comment from the Office of the Commissioner for Canada Elections.

Though few Canadians seem to be aware of this, the recent federal election campaign was fought under a new law that imposes severe penalties for publishing misleading statements on the internet during the writ period.

The new, amended Section 91 of the Canada Elections Act, which came into effect on September 11, threatens prison terms of up to five years and fines up to $50,000 for disseminating false information about "a candidate, a prospective candidate, the leader of a political party or a public figure associated with a political party."

Though an earlier version of the law required that the person charged be aware that the statement is false, the final version removed the word "knowingly" — and allows a charge to be laid even in a case of someone sharing a statement they believe to be true.

Even a cursory search of Twitter quickly turns up countless examples of Canadians who have posted statements that appear to violate the law.

Moreover, one of Canada's most mainstream political advocacy groups says it has pulled back some of the messaging it normally sends out every election cycle — out of a fear of potential punishment.

A response to a real problem

Section 91 is the main plank of the government's effort to prevent disinformation campaigns from distorting the Canadian political process the way Russian troll farms targeted the U.S. presidential election in 2016.

The law applies to both foreign and domestic actors, though critics have argued it would be difficult to enforce against groups or individuals outside Canada.

Joanna Baron, a lawyer and executive director of the Canadian Constitution Foundation, has launched a constitutional challenge of Section 91, arguing that it's an unreasonable restriction of free speech.

Baron said her group agrees with the aim of defeating efforts to sabotage the democratic process.

"That's a goal that we share, but we think this is an ineffective and overly draconian attempt to address it," she said. "Malevolent actors from Russia and China will not be deterred by a Canadian domestic law."

Baron says that one of the participants in her organization's lawsuit is the Canadian Taxpayers Federation, which dialled back some of its usual election advocacy work this time over concerns about aspects of the law.

"This law has already effectively chilled legitimate political speech," she said.

Elections Act, 91 (1) No person or entity shall, with the intention of affecting the results of an election, make or publish, during the election period, (a) a false statement that a candidate, a prospective candidate, the leader of a political party or a public figure associated with a political party has committed an offence under an Act of Parliament or a regulation made under such an Act—or under an Act of the legislature of a province or a regulation made under such an Act—or has been charged with or is under investigation for such an offence; or (b) a false statement about the citizenship, place of birth, education, professional qualifications or membership in a group or association of a candidate, a prospective candidate, the leader of a political party or a public figure associated with a political party.

CBC News asked Prime Minister Justin Trudeau about Section 91 during a campaign stop in Iqaluit. He said the government had struck the right balance with the new law.

"We're in a world right now where we've seen the impact of the kinds of polarization, the kinds of politics of misinformation, of fear and division ..." Trudeau said. "We have developed an approach that is going to be protecting Canadians from misinformation. We recognize that this is a careful line to walk and we will continue to walk it with Canadians."

'A cannon to kill a fly'

Aaron Wudrick is the national director of the Taxpayers Federation, a mainstream advocacy group that is supported by about 20,000 donors.

Wudrick said that while in the past he might have re-posted news stories online during an election campaign, he's reluctant to do so now because they might later turn out to contain errors that run afoul of the law.

"It's just deeply concerning that just in doing my job, repeating facts that I heard in the news, that I could be breaking the law," he said.

"We're a very loud advocacy group. We have strong opinions. We've had to be extra-careful. I double and triple-check. Some people might say that's a good thing. But it's a free speech issue.

"I understand we want to weed out lies, but if the price to do that is to chill free speech to the point where people don't think they can speak openly, I think that's a problem."

In an affidavit filed along with the CCF's lawsuit, Wudrick said that "the amendments to s. 91 of the CEA have resulted in the CTF's reducing its political communications planned for the election period.

"Usually, we would use social media advertisements and public events to promote our political message during elections. This year, partly out of a fear of the consequence of the amendments to s. 91, we have decided not to purchase Facebook advertisements on federal issues, and have ceased a campaign and disabled a website that focused on politicians that have broken promises to the public."

Commissioner won't pursue unwitting offenders

After this story was published, the Office of the Commissioner of Canada Elections contacted CBC News to say that, as the body responsible for enforcement, it did not intend to pursue cases against those who did not know they were stating or repeating false information.

"Our interpretation of the provision is that it requires proof of knowledge that the statement was false," said Michelle Laliberte, a manager at the commissioner's office. She said that although the word "knowingly" was removed from Section 91, "in our view, the inclusion of 'knowingly' in paragraphs 486 3(d) and 4(b) are redundant." In other words, Commissioner Yves Côté intends to treat the law as though the word "knowingly" were still there, implied.

Baron said that if the courts uphold that position, her organization's constitutional challenge will have essentially succeeded.

But she said that while she welcomes the interpretation chosen by Côté, it's only reassuring in the short term. "The Attorney General of Canada may take a different position on the law, as might a future commissioner, so it's important we go to the court for clarification," she said.

Baron said that the problem remains the wording of the law itself — particularly the decision to remove the word "knowingly".

"According to basic principles of statutory interpretation, a change in language means a change in meaning," she said. "Put differently, when interpreting statutory amendments, courts presume that they were not made in vain. In this case, the change in meaning is obvious: while the prohibition formerly applied only if the publisher of the false statement knew of its falsity, there is no longer any such knowledge requirement."

Baron said it's not hard to imagine a person falling afoul of the law during the last election without "knowingly" trying to mislead anyone.

"For example, if a member of the public were to tweet (based on his or her honest belief in the truth of the information) 'Vote for Andrew Scheer — he's got great business sense because he is a fully qualified insurance broker', he or she would have both unknowingly published a false statement about Mr. Scheer's 'professional qualifications,' as he did not, in fact, acquire a full insurance broker's licence, and intended 'to affect the results of an election,' as he or she made the statement for the purpose of influencing others to 'vote for Andrew Scheer.' Hence, the publisher of this statement would be liable to prosecution under s. 91(1), even though he or she did not know that the statement was false."

Case delayed

Baron said the CCF was hoping to have its case heard before the law came into effect.

"We brought the application forward on an urgent basis, arguing that it should be heard before this election because it has such a direct effect on speech during the election writ period. Not surprisingly, the attorney general disagreed."

The Ontario Superior Court accepted the government's argument that it needed more time. Baron said she hopes the case will progress now that the election is over.

She said the campaign saw clear examples of statements by candidates and parties that could have led to prosecution under the law — including suggestions that Prime Minister Justin Trudeau was under criminal investigation over the SNC Lavalin affair.

The Conservative Party tweeted — then deleted — that claim on September 17.

The Conservative Party first posted, then deleted, this tweet - which could violate the new Section 91 of the Canada Elections Act. (Twitter)

Section 91 makes it a criminal offence to proffer "a false statement that a candidate, a prospective candidate, the leader of a political party or a public figure associated with a political party has committed an offence … or has been charged with or is under investigation for such an offence."

Baron added that Conservative Leader Andrew Scheer's misleading description of his past as an "insurance broker" also could expose him to legal danger, since the law criminalizes any "false statement about the citizenship, place of birth, education, professional qualifications or membership in a group or association of a candidate."

"Political parties are among the entities who ought to be most concerned with this law," said Baron.

A law ripe for abuse

No charges have yet been brought under Section 91 relating to the 2019 campaign, but international experience shows that such laws have become a weapon for governments looking to silence online dissent.

Egypt and the Gulf states have aggressively prosecuted social media users over critical comments, using laws ostensibly intended to prevent disinformation.

Egyptian women's rights activist Amal Fathi was sentenced to prison last year under a law against "spreading fake news" after she posted a video exposing the reality of sexual harassment in the country. Bahraini activist Nabeel Rajab was sent to prison for five years for "disseminating false and malicious news" in social media posts criticizing the ruling family.

Baron said that while Canada is a democratic country, no one should feel overly reassured by the fact that Section 91 was not used during the campaign.

"One can debate whether the law would actually be used in these instances," she said. "But even if it never was, we're more concerned about the chilling effect, that people will soft-pedal their opinions and comments out of fear of these penalties of fines and imprisonment."

She said a rational citizen would want to be very careful with posts on the SNC Lavalin affair, for example.

"I don't know if that's the Liberals' intention, although certainly it is convenient to them."

Law defends politicians, not institutions

Section 91 has parallels with laws in other countries that aim to stifle criticism and dissent by making it a crime to insult or defame leaders.

Although the law is meant to protect Canada's elections, it does nothing to prevent any actor from targeting Canadian institutions — including the elections themselves.

Section 91 only criminalizes false statements that target politicians — "a candidate, a prospective candidate, the leader of a political party or a public figure associated with a political party."

So while an individual can be imprisoned under Section 91 for calling a politician a thief, there are no consequences for claiming Elections Canada plans to rig an election.

"Canadians should be free to viciously critique political leaders," said Baron. "That's essential to a healthy democracy.

"It's also kind of an implicit contract that when you make the choice to enter public life — you accept that you are going to be subject to criticism and some of it will be harsh."