Short answer. A court can apply custom to fill a legal gap, but only if the custom does not conflict with existing law, public order, or public policy. Article 11 of the Civil Code makes clear that customs contrary to law, public order, or public policy cannot be recognized — the custom must operate within those limits to be valid.
What the law says
Customs which are contrary to law, public order or public policy shall not be countenanced.
Civil Code, Article 11 — Customs Contrary to Law. Read the full provision →
Custom as a source of law in the Philippines
The Civil Code recognizes that written legislation does not cover every situation. When no statute directly addresses a dispute, the Code provides that custom may be applied. Article 11 does not grant unlimited authority to custom; it draws an essential boundary: a custom can be applied only if it does not violate existing law, public order, or public policy. Within that limit, custom functions as a legitimate gap-filler. A court presented with a situation the Code does not expressly address may look to established community practice as a guide to what is reasonable and just.
Three limits on custom
Article 11 identifies three tests a custom must pass. First, it must not be contrary to law — a custom that directs people to do something a statute forbids, or that permits what a statute prohibits, cannot be applied. Second, it must not be contrary to public order — the stable and orderly functioning of society and institutions. Third, it must not be contrary to public policy — the principles the State uses to protect welfare, morality, and the social fabric. A custom that fails any one of these three tests will not be recognized by the courts.
What 'contrary to law' means in this context
A custom is contrary to law when it directs conduct that statutory law expressly prohibits, or when it dispenses with requirements that the law makes mandatory. For example, a local practice of sealing an agreement with a handshake without any written record would not override a statute that requires a contract for the sale of land to be in writing. The enacted law takes priority; the custom cannot modify or circumvent it. A court that applies a custom to defeat the plain requirements of a statute oversteps the role Article 11 assigns to custom.
Proving the existence and content of a custom
When custom is invoked in a legal dispute, its existence and content must be proven — courts do not take judicial notice of local customs the way they do of enacted law. The party relying on the custom must establish that the practice is followed consistently, that it is observed as a rule by the community rather than as a mere preference, and that it predates the dispute. Without adequate proof, the court cannot apply the custom, and the case must be decided on whatever analogous statutory principles or general principles of law and equity are available.