Does Costco ever reject returns?

As a consumer, I'm often curious about the return policies of retailers, especially when it comes to larger purchases or items that may be subject to special conditions. So, I have to ask, does Costco ever reject returns? I've heard great things about their satisfaction guarantee, but I'm just wondering if there are any instances where they might decline to accept a return. It would be helpful to know what kinds of products or situations might be exempt from their generous return policy.