Two dozen groups who aren't registered as third parties under Ontario's election rules have been quietly targeting Ontario voters with Facebook ads on a range of issues during the provincial election campaign, CBC News has learned.

Under Ontario election rules, any group running political ads during a provincial election has to register as a third party once it spends more than $500. Knowingly contravening the rules can result in fines of up to $5,000.

To date, 53 groups running Facebook ads during the campaign have registered with Elections Ontario. However, a review of ads by CBC News reveals that two dozen groups are running advocacy or campaign ads without having registered with Elections Ontario as third parties.

CBC has partnered with ProPublica, a non-profit U.S-based investigative journalism organization which developed a Facebook ad collector. The collector gathers ads from the Facebook feeds of people who agree to download its browser extension.

ProPublica's Facebook ad collector allows CBC News to see the ads running on Facebook — and to determine which voters the ads are targeting.

Some of the groups running the ads have proven to be difficult, if not impossible, to trace. For example, Ontario for Ontarians is running 10 different Facebook ads – generally attacking Progressive Conservative Leader Doug Ford. But the group's Facebook page and its accompanying website, www.notdoug.com, give no indication of the source of funding for the ad campaign.

This is one of several Facebook ads being run by the unregistered group Ontario for Ontarians. (Facebook)

The only contact information for another group, Vote For Our Children, is a "send message" button on its Facebook page. It did not respond to messages from CBC News.

Vote For Our Children is running an ad attacking Ontario's sex ed curriculum and praising Ford. The ad targets voters between the ages of 35 and 60 who live near Toronto. A second ad being run by the group supports Roshan Nallaratnam, the PC candidate in the Toronto-area riding of Scarborough Guildwood.

It is not known whether either Ontario for Ontarians or Vote For Our Children has spent more than $500.

Most of the other unregistered groups — which include professional associations, unions and private companies — are more open about who they are and what they are doing. Some, like the Ontario Confederation of University Faculty Associations, say they haven't registered as third parties because they haven't yet spent $500 during the campaign.

The Ontario Pharmacists Association is running a $100,000 Facebook ad campaign during the election - but says it doesn't have to register as a third party because the campaign doesn't favour a particular candidate or party. (ProPublica Facebook ad collector)

Others — like the Ontario Pharmacists Association, which is running a $100,000 Facebook ad campaign it says has reached more than 250,000 Ontarians — say they don't think they have to register. The OPA says its campaign calling for pharmacists to have the power to prescribe medication for common ailments doesn't favour any particular party or candidate.

The Windsor-based company Border Connect ran this ad referring voters to an NDP website. (ProPublica Facebook ad collector)

Others groups are remaining tight-lipped. Border Connect — a Windsor, Ontario based e-manifest technology company which has not registered as a third party — ran ads to promote advance voting which included an Ontario NDP logo and a link to an NDP website. Company CEO Daniel Dent decided to run the ad; he declined to be interviewed or to say whether the company spent more than $500.

Ads placed in traditional media like newspapers, radio and television are viewable by everyone, which makes it easier for election authorities to monitor them.

Social media sites like Facebook allow advertisers to microtarget ads to particular voters or groups, making them very difficult to see — unless you are part of the demographic being targeted or continually monitor a page with Facebook's ad viewer pilot project, which is available only in Canada.

Elections Ontario refuses to say what it is doing to monitor social media ads, whether it has received any complaints or whether it has launched any investigations.

The ProPublica ad collector also provides a glimpse into potential grey zones in Ontario's elections rules when it comes to social media advertising by third parties.

For example, while one expert might see an advocacy ad as political enough to require the group running it to register, another might give the group a pass if the ad stops short of openly supporting or opposing particular parties or candidates.

A number of paid Facebook ads also use news stories to try to advance a party or a group's viewpoint. A group or candidate with a political agenda might place an ad linking to a news story or column — but Ontario's election law says transmitting things like an editorial, a column or a commentary on the news doesn't constitute political advertising.

Duff Conacher, co-founder of Democracy Watch, said that could prove problematic for elections officials.

"Elections Ontario should have been much more clear and will have difficulty going after some of these groups after the fact, because they'll be able to say commentary, news, the transmission of a column, an editorial, a letter are exempted and we interpreted them to include pushing a newspaper article that was already published out there," he said.

The role of Facebook in political campaigns has been in the spotlight in recent weeks following the revelation that the firm Cambridge Analytica used Facebook data on individuals in an attempt to influence voters.

Facebook has moved since then to try to increase transparency. For example, it is running a pilot project in Canada that allows voters for the first time to view the ads a given Facebook page is running – although it doesn't tell you who is being targeted.

Given the way Facebook prices its ads — sometimes through auctions — it can be difficult to know exactly how much a group might have spent during an election campaign. However, a group could tell Facebook to run $499 worth of ads, staying just below the $500 limit.

Facebook officials say they plan to eventually release spending information for political ads, but that won't be available for the current Ontario election campaign. They also say they plan to label ads that are political or issues-based during elections, and to maintain an archive going back four years.

Tamara Small, associate political science professor at the University of Guelph, says ads should mention a party, a leader or a candidate to be considered political. (University of Guelph)

Experts seldom agree on what constitutes a political ad. Tamara Small, associate professor of political science at the University of Guelph, said an ad should clearly support a party or a candidate to be considered political advertising. She said she doesn't believe the law is intended to cover issues-based advertising that isn't linked to a party platform.

"Something like health care, I think the law is not meant to capture all of that."

Conacher, however, said he believes that the ads being run by 22 of the 25 unregistered groups constitute political advertising.

Conacher said Elections Ontario should clarify the rules about what constitutes political advertising.

"Elections Ontario is the front line enforcement agency which decides whether to prosecute someone," he said. "And they should have done much more to define what is not covered by the political advertising definition that limits what third parties are allowed to do."

Elizabeth Thompson can be reached at elizabeth.thompson@cbc.ca