In the US, all new retail products purchased by consumers come with an implied manufacturer's warranty, even though the retailer might exclude certain items from the store's warranty policy. (Whether or not it applies here, technically, depends on whether that crack renders them "unfit" for their purpose, but don't get bogged down in that legal detail and ignore that for right now.)
I don't believe that CCM mentions anything about "pro stock" in its 90-day warranty for defects. They only seem to exclude gear purchased as part of team sales to professional and college teams. I don't know if it's the case that, by definition, anything marked pro stock had to have been ordered as part of a team sale, originally; but even if that's the case, I'd still contact them at warrantyccm@ccmhockey.com and just tell them you found a crack in a brand new pair of shin guards and attach a scanned photo of the receipt and see what they say. If they tell you to contact the retailer, let them know that the retailer said that you need to contact CCM. Tell them that you've been using CCM equipment exclusively for your entire hockey career without any issues, and that you'd appreciate it if they would just do the right thing for a loyal retail customer who bought one of their products that clearly has a manufacturing defect. Don't be surprised if they offer a resolution to avoid alienating a loyal retail customer, regardless of any policy about pro stock warranties. Nothing to lose but the time it takes to send an email.