Customs under civil law (Articles 11, 12)

Customs which are contrary to law, public order or public policy shall not be countenanced. A custom must be proved as a fact, according to the rules of evidence. ( Articles 11 and 12 of the New Civil Code of the Philippines)

A custom is a rule of human action (conduct) established by repeated acts, and uniformly observed or practiced as a rule of society, thru the implicit approval of the lawmakers, and which is therefore generally obligatory and legally binding. (Paras) Stimson’s Law Dictionary defines a custom of a place as that which is brought about by local usage, and is not annexed or peculiar to any particular individual.

A shorter definition of custom would be that it is a rule of conduct imposed not by any written law but by social pressure. Such social pressure achieves the status of a "custom" if there is uniform compliance among members of the community who view it as obligatory. As a result of their opinion as to the custom's obligatory nature, there is proof that said members repeatedly comply with such rule of conduct.

Since the Philippines is a civil law country, the legal system heavily relies on written laws passed by Congress and approved by the President. As a general rule, customs cannot be the basis of obligations as the Civil Code squarely answers by saying: "Article 1157. Obligations arise from: (1) Law; (2) Contracts; (3) Quasi-contracts; (4) Acts or omissions punished by law; and (5) Quasi-delicts." Therefore, courts, as a rule, cannot consider customs in deciding a case.

However, if the following requisites are present, courts are justified in considering custom in deciding a case:

1. Allegation and proof of the existence of such custom;
2. Consistency with law;
3. Consistency with public order and public policy; and
4. Belief and (juridical) intention of the community to make the conduct as obligatory as a law (also known as convictio juris seu necessitates; in international law, this is called opinio juris sive necessitates).

Proof of the existence of the custom should include:

1. Evidence of repeated compliance with such custom;
2. Evidence of the community members' uniform compliance with the custom; and
3. Evidence of lapse of sufficient time (which further proves existence and due observance).

Belief or intention of the community to made the custom as binding as law is shown by the existence of punishments or consequences that would befall anyone who disregards or violates said custom.

For example, a custom that endangers life or property cannot be countenanced. In one case, the Supreme Court wrote:

Basing himself on this alleged custom, counsel contends that "When a person does what is usual and customary, i. e., proceeds as he and others engaged in a like occupation have been accustomed to proceed, the action cannot be characterized as reckless, nor, strictly speaking, as negligent." To this the obvious reply may be made, for the moment admitting the existence of the custom, that a practice which is dangerous to human life cannot ripen into a custom which will protect anyone who follows it. To to upon a railroad crossing without making any effort to ascertain the approach of a train is so hazardous an act and one so dangerous to life, that no one may be permitted to excuse himself who does it, provided injury results. One who performs an act so inherently dangerous cannot, when an accident occurs, take refuge behind the plea that others have performed the same act safely. (Yamada v. Manila Railroad Co., G.R. No. 10073, December 24, 1915)

A custom that allows the dissolution of marriage and, thereafter, remarriage without compliance with the processes required by law also, therefore, cannot be countenanced since such is against the Family Code and the Revised Penal Code.

In another case (Martinez v. Van Buskirk, G.R. No. 5691, December 27, 1910), it was held:

It appears from the undisputed evidence that the horses which caused the damage were gentle and tractable; that the cochero was experienced and capable;  that he had driven one of the horses several years  and the other  five or six months; that he had been in the habit, during all  that time, of leaving  them in the condition in which they were left on the day  of the  accident; that they had never run away up to that time  and there had  been,, therefore, no accident due to such practice; that to leave the horses and assist in unloading the merchandise in the manner described on the  day of the accident was the custom of all cocheros who delivered merchandise of the character of that which was being  delivered  by the  cochero  of the  defendant on the day in question, which custom was  sanctioned by  their employers. In our judgment, the  cochero of the  defendant was not negligent in leaving  the horses  in the  manner  described by the evidence in this case, either under Spanish or American  jurisprudence.   (Lynch  vs.  Nurdin, 1 Q. B.,  422; Rumsey vs. Nelson, 58  Vt., 590; Drake vs. Mount, 33 N. J. L., 442;  Hoboken Land and Improvement  Co.  vs. Lally, 48 N. J. L., 604; Wasmer vs. D. L. & W.  R. R. Co., 80 N. Y., 212.)