In the dead of summer, when most people weren’t watching, a Tory government intent on beefing up its economic bona fides quietly made it more difficult for immigrants to make a new home in Canada. Thousands of young adults who used to qualify as dependents can no longer make the trip on their parents’ coattails. The move, which took effect on Aug. 1, has upset advocates for immigrants and refugees and sparked the latest round in an ongoing feud between the governing party and its critics at the Canadian Bar Association.

Until the end of July, children of new immigrants could apply as dependents until they turned 21. The new rules set the ceiling at 18. The rationale is that kids who arrive in Canada earlier can benefit from a Canadian education, and ultimately offer more to our fragile economy than their older counterparts.

It’s a change the Tories spent two years trying to make. Jason Kenney, then minister of citizenship and immigration, first raised the idea during public consultations in spring 2012, when he was coming up with a tighter approach to family reunification. A year later, at a press conference in Mississauga, Ont., he dismissed dependency rules as “peculiar.” He was speaking that day about dependents in their late 20s and 30s who used to qualify if they enrolled in a post-secondary program. “You’re not a child anymore. You’re an adult. Take responsibility for yourself,” Kenney said. “Come as a tourist. Apply for permanent residency. Apply for immigration as an independent economic immigrant. You’re more than welcome, but come as an independent immigrant.”

The new rules disqualify those so-called freeloaders, but they reach far deeper and target 19-year-olds who might be barely out of high school, and children of potential refugees who scramble for resettlement. Federal data suggests 7,832 eligible dependents in 2012 were older than 18 years of age—about 10 per cent of all dependent children under the old definition. The only ones from that group who would now qualify are applicants between 19 and 22 who suffer from a mental or physical disability.

The government argued its case in the Canada Gazette last year. “Statistics demonstrate that older dependent children have lower economic outcomes over the long run,” read its analysis, which pointed out that 66,782 applicants in 2012 would still qualify now.

Kenney eventually moved into a different portfolio, but the policy survived, despite the waves of disagreement sparked by a second consultation last year. Sixty submissions largely opposed the change. The Canadian Council for Refugees (CCR) warned the policy would break apart families and leave defenceless dependents in unsafe conditions. Loly Rico, the CCR’s president, told Maclean’s that Conservatives who have kids ought to know better and “really don’t have a heart.” Mario Bellissimo, chair of the bar association’s national immigration law section, says a purely economic rationale allows government to exert more control over who settles in Canada, but damages the country’s immigration model because every potential dependent left behind could provide a benefit down the line. “You’re looking at economic units entering Canadian society without the societal supports that you might later have from individuals that surround you—and might support you through times of sickness, child rearing, job loss,” he says.

There’s an economic cost to shutting out a pool of young adults. “Canadian employers need to find new entrants into the labour force,” says Dan Kelly, president of the Canadian Federation of Independent Business, “and often kids that come with their parents will look for a job.” There’s another question that remains unanswered, which is how much of a difference those three years make. A seven-year-old might assimilate much more quickly than a child of 21, but how much better does one adapt at 18 than at 20?

Kenney declined to speak to Maclean’s for this story, but Arthur Sweetman, an economics professor at McMaster University and co-author of a 2001 paper referenced in government analyses, says immigration toward the end of high school is “disruptive”: learning a new language is difficult at that time, and younger kids are better at bridging a quality gap between two countries’ education systems. But he admits older kids are often able to overcome those challenges.

It’s too early to tell how many families will be forced to split apart or build new lives elsewhere, or what the cost to our economy will be of losing skilled-worker parents. Bellissimo has only anecdotal evidence of impact on families. Rico says she’ll know more in six months. Meanwhile, the Tories seem focused on their economic message. It’s unclear how the hard-won immigrant vote will respond to the change, but the economy-first mantra is a political position the Tories plan to ride all the way to the voting booth.