Just because Costco put the new tires on the back doesn't mean you can't rotate them to the front. I suspect it's just store policy, and not law that the better tires must be on the back, though I don't specifically know Alberta laws.
There is a little bit of sense to the recommendation to have good traction in the back, but the need for it in my humble opinion is often overstated for many modern vehicles. A lot of cars are so biased towards understeer that it's hard to get them to oversteer under most any circumstances. Modern electronic stability control systems also help here. There are practical advantages to having the better tires on the front of a front-wheel-drive vehicle, too, such as being better able to climb snowy hills.