That's true, I assumed from your original comment where you said "directly from a company in the primary supply chain of the shoe company" that the shoes were from further up the supply chain, like a factory, rather than further down. My mistake.
Even if the product were from an authorized retailer, I don't see how the shoe company's request to Amazon was illegal. Restraint of trade means that contracts restricting commerce are in some cases unenforceable. It doesn't mean that Amazon is compelled to do business with the reseller if they would rather prioritize their relationship with the shoe company.
