Short answer. By an official publication of the record, or by a copy attested by the officer with legal custody. Because the record is kept abroad, the copy must also be accompanied by a certificate that the officer has custody, in the form the applicable treaty or the consular route requires.
What the law says
may be evidenced by an official publication thereof or by a copy attested by the officer having the legal custody of the record, or by his or her deputy, and accompanied, if the record is not kept in the Philippines, with a certificate that such officer has the custody
Rule 132, Section 24 — Proof of official record. Read the full provision →
What the law says
the certificate may be made by a secretary of the embassy or legation, consul general, consul, vice-consul, or consular agent
Rule 132, Section 24 — Proof of official record. Read the full provision →
Two ways to put the record before the court
Section 24 of Rule 132 gives two routes for proving the record of a public document. The record may be evidenced by an official publication thereof, or by a copy attested by the officer having the legal custody of the record, or by his or her deputy. The attested copy is the ordinary route in practice, because most foreign records are not published in a form a litigant can simply produce. What matters is that the attestation comes from the officer who has legal custody of the record, not from whoever happened to hand you the document.
The custody certificate for records kept abroad
The additional requirement is what distinguishes a foreign record from a local one. Where the record is not kept in the Philippines, the attested copy must be accompanied with a certificate that such officer has the custody. So two separate things travel with the document: the attestation by the custodian that the copy is correct, and a certificate establishing that the person attesting is indeed the custodian. Litigants regularly obtain the first and overlook the second, and the omission is the more common reason a foreign record runs into difficulty.
The treaty route and reciprocity
Where the office holding the record is in a foreign country that is a contracting party to a treaty or convention to which the Philippines is also a party, or where the document is considered a public document under such a treaty or convention, the certificate or its equivalent shall be in the form prescribed by that treaty or convention, subject to reciprocity granted to public documents originating from the Philippines. The section also provides that the certificate is not required at all where such a treaty has abolished the requirement or exempted the document itself from the formality.
The consular route, and the effect of compliance
For documents from a country that is not a party to such a treaty, the section keeps the older path. The certificate may be made by a secretary of the embassy or legation, consul general, consul, vice-consul, or consular agent, or by any officer in the Philippine foreign service stationed in that country, authenticated by the seal of his office. The payoff for doing this correctly is stated in the same section: a document accompanied by the certificate or its equivalent may be presented in evidence without further proof, the certificate being prima facie evidence of due execution and genuineness.