It is nowadays widely recognized that constitutive rules play a key role in social ontology. Their definitional character is the primary source of the meaning of every rule-based activity, but what can ensure the persistence of this activity? The most common reply found in literature is to rely on social acceptance; even though this is certainly true, it is nonetheless not sufficient to explain what happens in breakdown situations, i.e. when by following constitutive rules institutions end up in an impasse. It is in a sense necessary to embed in the system something that would preserve it from destruction. Our claim is that for this purpose an arbitral function is needed. Intuitively, an arbitral function is a mechanism which is - at least partially - extra-contextual, that is introduced in a system to solve possible or actual impasses. This function may equally well be played by an intentional agent, or by an extra-contextual rule. Examples of the former case are: a referee in a football game, an arbitrator in a legal conflict, a judge exerting discretion in court; examples of the latter are: the toss in sport games, and the 50-move rule in chess. Our contribution then amounts to: introducing a novel concept, that of arbitral function; showing it is widespread in institutional reality; moreover, that it is essential in every institution. Finally, if constitutive rules determine that a certain activity counts as a valid element of an institution, arbitral functions are what ensures that this activity persists in being an element of that institution, by preventing possible impasses.