Affidavit of Foreign Law

Affidavit of Foreign Law. When a Thai court or administrative body must apply a foreign legal rule—e.g., to decide whether a foreign divorce is valid, how a foreign company is constituted, or whether an overseas inheritance rule applies—it commonly relies on an Affidavit of Foreign Law (also called a foreign-law opinion, certificate, or expert statement). This document explains, evidence-by-evidence, what an affidavit of foreign law is, who should prepare it, how it should be drafted and authenticated for use in Thailand, how Thai courts treat it, and a practical checklist and model language you can use to brief counsel or an overseas expert.

What an Affidavit of Foreign Law is — function, not form

An affidavit of foreign law is a sworn statement (or an expert opinion) setting out what the law of another jurisdiction is and how it applies to a particular fact pattern. It is not evidence of facts (those must be proved separately) — its sole purpose is to inform the Thai decision-maker of foreign substantive law or foreign procedural rules.

Typical uses in Thailand:

proving the validity or effect of a foreign marriage, divorce, or adoption when family or immigration issues arise;
proving corporate capacity, authority or corporate form for foreign companies in commercial transactions or to register a foreign company’s branch;
establishing probate, succession or inheritance rules from another country when an estate or property issue touches Thailand;
clarifying foreign criminal status (convictions, pardons) for sentencing, deportation or character evidence;
supporting conflict-of-laws submissions where Thai law defers to foreign law on a specific issue.

Who should prepare it — the competent author

An affidavit of foreign law should be prepared or sworn by a qualified foreign legal practitioner (barrister, solicitor, attorney) or by a foreign law academic who has proven competence in that country’s law. The important points:

the person must state their qualifications and experience, identify sources consulted (statutes, cases, commentaries), and explain the research method;
the affidavit should be fact-sensitive: it should explain the applicable legal rule and, where relevant, give an opinion on how that rule applies to the case’s facts;
where possible, use an author who can swear the affidavit before a notary public or a court in the foreign jurisdiction (this assists authentication); and
in high-stakes matters, Thai parties sometimes retain two complementary pieces of evidence: an opinion letter and a sworn affidavit from the same expert (one analytical, one notarized).

Essential content and structure — what Thai courts want to see

A robust affidavit of foreign law typically contains:

Introduction & authority — the expert’s full name, professional qualifications, bar/admission reference, practicing address and contact details.
Scope & instructions — who instructed the opinion, the question(s) posed, and the facts assumed (is it limited to law, or does it also accept certain agreed facts?).
Statement of sources & method — list the statutes, reported cases, unreported decisions, government guidance and secondary sources consulted and the databases used.
Clear statement of the foreign law — succinct propositions of law, numbered for easy citation, each followed by references to primary sources (case names, statute sections).
Application to facts — a reasoned application section that explains how the law maps to the case’s factual matrix. Distinguish matters you treat as fact (assumed) from legal inferences.
Limits & caveats — identify unsettled issues, conflicting authorities, or areas where courts diverge; explain whether practice varies by region within the foreign jurisdiction.
Sworn attestation — a clause sworn before a competent officer (notary or court officer) stating the statement is true to the best of the affiant’s knowledge.
Exhibits — copies of the foreign authorities cited (cases, statutory extracts) with translation where necessary.

Include a short, neutral bibliography and, where relevant, a one-paragraph summary of the conclusion for quick reading by judges or registry staff.

Authentication & legalization — making it admissible in Thailand

Thai courts and administrative bodies require that documents originating abroad be properly authenticated. Practical steps:

Notarization: have the expert sign the affidavit before a local notary public in the foreign country.
Apostille or consular legalization: if the foreign country is a Hague Apostille Convention member, obtain an apostille from the issuing authority. If not, obtain consular legalization from the Royal Thai Embassy/Consulate after any necessary foreign-ministry certification.
Official translation: prepare a certified Thai translation of the affidavit and all cited foreign authorities (Thai courts expect Thai language evidence unless they explicitly accept English). The translator’s statement should be signed and, where required, notarized and legalized (or accompanied by an apostille).
File originals: file the original affidavit (or a certified copy) and the Thai translation with the Thai court or authority, together with the apostille/consular certificate. Some courts accept scanned copies in early stages but will insist on originals for final hearings.

Note: for affidavits sworn in certain jurisdictions, the home-court apostille plus a certified translation is sufficient. Always check the specific registry practice of the Thai court or government department handling your matter.

Weight and cross-examination — how Thai courts treat them

In Thailand, an affidavit of foreign law is evidence of the foreign legal rule but the court is the ultimate arbiter of how persuasive it is. Practical points:

Thai judges often accept well-reasoned opinions from recognized foreign counsel, especially if primary sources are provided and translated.
Where the other side disputes the foreign law, the court may permit competing affidavits (two experts) and, in contentious litigation, order an expert conference or allow cross-examination of the foreign expert (usually via video link or through a local Thai expert).
When foreign law is unsettled, courts prefer caution: highlight conflicting authorities and explain why a particular line is preferable.

Practical timeline, fees and risks

Timeline: obtaining a well-researched affidavit usually takes 1–4 weeks (longer for complex or obscure jurisdictions). Allow additional time for notarization, apostille/consular legalization and Thai translation (another 1–2 weeks).
Cost: expert fees vary hugely by jurisdiction and expert seniority—budget from several hundred to several thousand USD plus notarization and legalization costs.
Risk: avoid relying solely on unsigned opinion letters; properly sworn and authenticated affidavits reduce the risk of inadmissibility or challenge.

Best practice checklist — ready to use

☐ Instruct a qualified foreign lawyer or academic with verifiable credentials.
☐ Provide the expert with an agreed, concise statement of facts to be assumed.
☐ Ask the expert to cite primary authorities and provide those materials as exhibits.
☐ Require the expert to sign the affidavit before a local notary (or appropriate judicial officer).
☐ Obtain apostille or consular legalization from the Royal Thai Embassy (as required).
☐ Order a certified Thai translation of the affidavit and exhibits; legalize the translator’s certificate if requested.
☐ File originals and translations at the Thai registry and keep certified copies for service.
☐ If the opposing party may contest foreign law, consider appointing a rebuttal expert pre-emptively.

Sample short affidavit clause (illustrative)

“I, [Full name], Barrister/Solicitor admitted in [jurisdiction], of [address], being duly sworn, say: I am competent to give the opinion stated herein. I have been instructed by [party] to advise on the law of [jurisdiction] on the validity of [issue]. My opinion is formed on the basis of the documents and authorities listed in Annex A, and the facts assumed in Annex B. I verily believe the matters stated in this affidavit to be true.”

Final practical note

An affidavit of foreign law is not mere paperwork; it is the bridge that enables Thai decision-makers to apply foreign legal rules accurately. Invest in a qualified, well-documented and properly legalized affidavit early in your case. Doing so reduces delays, strengthens admissibility, and increases persuasive force—particularly when you provide authoritative translations and primary sources.