The pen's barrel is made up of several powerful cylindrical magnets, which can be taken apart and snapped together in different ways, as this video shows.
There's no practical benefit to the Polar Pen. It's more of a conversation piece and time waster.
The problem, as far as health officials were concerned, was the prospect that children might pop one or more of those little magnets in their mouths.
"The results of swallowing small powerful magnets can be very serious and life-threatening," says the cease-and-desist letter Health Canada sent to Gardner, according to CBC News.
"Swallowing incidents have often resulted in considerable damage to the gastrointestinal tissues and required emergency surgical treatment and extended hospitalization. For survivors, there can be serious long-term health consequences."
Health Canada last May banned the importation and sale of Chinese-made Buckyballs, magnetic toys made of the same rare earth material used in the Polar Pen.
"Unlike other small objects that would be more likely to pass normally through the digestive system if swallowed, when more than one small powerful magnet is swallowed, the magnets can attract one another while travelling through the digestive system," the department's health alert says.
"The magnets can then pinch together and create a blockage and slowly tear through the intestinal walls, causing perforations."
The letter, which contains much the same wording as the Buckyballs recall, gutted Gardner's plans. He's managed to raise more than $800,000 via Kickstarter, the crowd-sourcing investment site to begin manufacturing the pen.
He told CBC News he'll now have to refund that money, including pen pre-orders at $35 to $40 each, and he stands to lose the $100,000 he's already put into the project.
"We've pushed forward to start manufacturing here in Waterloo," he said. "So now we have basically a hundred thousand dollars invested into producing products for people that have bought it and now we feel we will probably have to [give them a] refund."
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According to the U.S. web site Natural News, Gardner told a CBC interviewer he thought the ban was hypocritical.
"The funny thing is, is you can buy these magnets in any local hardware store," Gardner said. "There are actually three retailers in Waterloo that retail magnets very similar, if not even smaller."
It's not clear whether Gardner might move his venture out of Canada, hoping to make and market the Polar Pen abroad. It's worth noting the U.S. also banned Buckyballs after some children were hospitalized, so presumably Polar Pens would face the same prohibition as in Canada.
While it's unfortunate Gardner's enterprise has been cold-cocked by regulators, Health Canada seems to have made the right call here.
It's not as if the Polar Pen is a product that will change the world. It's an adult toy, essentially, and prudence dictates that children's health take precedence over our amusement.