The story of Health Canada’s reported plan to mount an advertising campaign this fall on the dangers of using marijuana, aimed at young people, is being spun two ways—both, at first blush, reasonably plausible.

Critics of the Conservatives suspect the ostensibly non-partisan public-health messages are really being concocted to support Tory attacks on Liberal Leader Justin Trudeau over his proposal to legalize and regulate marijuana.

Health Minister Rona Ambrose’s office counters that discouraging marijuana use, far from being motivated by such transient political aims, is fully consistent with the government’s long-standing approach under what is called the National Anti-Drug Strategy.

One piece of evidence that might back up Conservatives’ claim that the planned ad campaign flows from a well-defined strategy—and isn’t a recently improvised element in their assault on Trudeau’s position—would be any planning document that proves such ads were envisioned long in advance.

To see if these ads were expected to be part of the anti-drug strategy this year, I looked up what’s called the “Report on Plans and Priorities” for this “horizontal initiative” (the term for a federal program that spans more than one department, in this case, Health and Justice). The 2013-14 report itemizes $570.1 million to be spent under the strategy from 2012-13 to 2016-17. Health Canada’s section specifies the expected costs of everything from community initiatives and treatment programs, to First Nations programs and support for enforcement activities.

But nothing is earmarked for advertising. And that stands in sharp contrast to the same document for 2011-12, the final year of the first five-year iteration of the federal anti-drug strategy. In that report, $29.5 million is clearly allocated for Health Canada’s “mass media campaign (prevention action plan)” over five years, and $6.9 million is broken out for ads in 2011-12.

In fact, the government did produce and air advertising, including high-profile TV ads, during that first five years of the anti-drug strategy, under its “DrugsNot4Me” program. But the advertising component was eliminated in 2012 and, afterward, no more money was set aside under the strategy for further mass media campaigns.

Asked about where the money for any new ads will come from, Health Canada officials noted that the government’s Central Advertising Fund “is the primary source departments use to support government campaigns.” Indeed, the most recent report on that central fund, detailing allocations made from April 1 to June 30, shows $5.5 million being given to Health Canada for a campaign on “prevention of illicit drug use.”

That clears up how the planned ads will be paid for. But it doesn’t explain why the latest five-year plan for the anti-drug strategy failed to mention any mass media campaign, even though the previous five-year blueprint did so.

It seems clear that starting in 2012, advertising was no longer deemed essential to the anti-drug strategy. That lasted until the government revived it, perhaps sometime this past spring, as a matter of discretion. So what changed between 2012 and 2014 to make advertising on the dangers of marijuana a newly pressing public-health priority?