They can't. OTOH, limitations on exclusive rights in trademarks (or any other form of IP) vary a lot by jurisdiction, and within a jurisdiction over time; its fairly common for organizations to state policies where the domain of things for which permission is stated to be required overlaps the area of limitations on the right in question; to the extent those overlap, the stated policy has no effect, it only has effect in the intersection of the area where the company asserts a restriction and the area where local law gives the company control.