European governments are now spending at a rate that makes the maintenance of equipment, rather than its purchase, the decisive industrial question of the decade. A fleet that has been bought must be kept flying, driving and shooting, and the work of keeping it so is recurrent, labour-intensive, geographically fixed and politically visible. It is therefore natural to treat in-service support as the most accessible part of the defence market: the demand is certain, the technology is mature, the facilities are domestic, and the political appetite for local work is strong. That reading is mistaken in a specific and consequential way. Demand generated by a fleet does not by itself create a market a supplier can enter. Authorised sustainment is a permissioned activity, and the permission is granted by several different parties, in several different forms, each of which can be withheld. The question that follows is narrower and harder than the one usually asked: on what conditions does authorised in-service support become a durable route into European defence, and how far does moving that activity onto European soil change either the security of supply or the customer’s freedom of action? Three national cases and two regulatory frameworks, examined through documents that the state and the firms themselves have published, give an answer that is neither optimistic nor dismissive, and that has a definite shape.