That's simply because the 51% rule is based on cost, not content. It was never designed for food. It was presumably for something like importing T-shirts from Asia and then putting on some crests or doing some embroidery. If 51% of the costs are incurred here, you can call it “Product of Canada”--rather than the basic T-shirt or the cotton. If you want to have a direct impact, change that. If it was more than 80% or 90%, you'd probably cut out most of these things where people think that people have been misled.
As far as “Grown in Canada” goes, people use that now. There's absolutely no prohibition against using “Grown in Canada” now. In fact, it surprises me that people don't use it more. It's partly because of the integrated nature of our food system and partly because of our climate. But if someone had “Grown in Canada” on their label today and it wasn't grown in Canada, a single competitor complaint, a single consumer complaint, would go to the Food Inspection Agency. They have 6,000 or 7,000 people there. I am sure that somebody would be sent out to do one of their thousands of investigations. If it was clear that the product was not grown in Canada, they would take one of their many very significant enforcement powers to stop that. It happens every day.
I don't see any reason why you would have any mandatory rules about using “Grown in Canada”. If it's not grown in Canada, it's misleading; therefore under subsection 5(1) of the Food and Drugs Act you could stop its importation. You could seize and detain the product. You couldn't require a recall, but increasingly these days—and I spend a lot of time doing this—they end up talking to the big retailers and they have a product withdrawal, even though it isn't a public health problem.
So we have all the law we need to deal with somebody calling something “Grown in Canada” if it wasn't grown in Canada. There's absolutely no need for any regulatory change to deal with that.