Are you a lawyer or a random nobody?
This kind of ToS clauses are generally binding in pretty much every western jurisdiction. In fact, the clause may not even be necessary in e.g. EU because distance selling directive (Directive 97/7/EC) defines when and under what conditions the consumer has the right to cancel or rescind the contract. Unless a law or a contract term stipulates otherwise, there the buyer has no right to return a product, at least initially (the seller first has the right to provide a non-defective one or to repair the original). It's certainly possible that the ECJ will later elaborate more on these rights, but as it is the ToS clause is perfectly legal and enforceable. I think the directive sets the minimum level of protection, but I believe no EU provides wider protection than the directive, perhaps Germany aside. In fact, the specific clause, as it applies to EU, uses the same terminology as the directive.