Can a supplier decide whether a veterinary medicine is prescription-only?

No. Supply classification is set by the destination jurisdiction and may depend on active substance, route, species, indication, food-chain considerations and local antimicrobial policy. A product sold over the counter in one country may be prescription-controlled in another. Buyers should verify current classification with the competent authority or qualified local adviser and reflect it in channel design, promotion, ordering, storage and record-keeping.