Affidavit of Foreign Law

Affidavit of Foreign Law. When a Thai court or administrative body must apply the law of another country, an affidavit of foreign law is the primary way to prove what that foreign law is and how it should apply to the facts at issue. Confusing this with factual evidence is a common mistake: an affidavit of foreign law explains legal rules and offers reasoned application to agreed facts — it does not prove the facts themselves. This guide gives a practitioner-focused walkthrough: purpose, who should prepare it, the content and structure that persuades Thai decision-makers, authentication and translation steps, likely procedural uses in Thailand, timing and costs, and a practical checklist and sample wording you can use to brief an overseas expert.

Why courts need an affidavit of foreign law

Thai judges apply Thai conflict-of-law rules when a dispute touches foreign legal relationships (validity of a foreign marriage or divorce, corporate capacity under foreign corporate law, validity of foreign wills, foreign insolvency consequences, or the legal effect of foreign court orders). Because judges are not presumed to know the intricate law of every other jurisdiction, they rely on expert evidence — typically an affidavit sworn by a competent foreign lawyer or law professor — to explain:

what the foreign statutory rule, case law or practice is; and
how that rule applies to the particular factual matrix before the court.

A well-drafted affidavit of foreign law saves time, reduces cross-examination, and increases the affidavit’s persuasive power.

Who should prepare it — competence matters

Prefer an author who is:

a practicing lawyer admitted in the foreign jurisdiction (barrister/solicitor/attorney), or
a recognized academic or specialist with proven publications or case experience in the area of law concerned.

The affiant should state credentials clearly (admission year, practicing address, notable cases or publications). If the matter is particularly complex or novel, consider using two complementary experts (one academic, one practitioner) to cover both doctrinal exposition and practical application.

Core structure — what Thai courts want to see

A persuasive affidavit of foreign law is methodical and transparent. Include these sections, clearly labelled and numbered:

Introduction & qualifications — full name, firm/university, practicing or academic credentials, and a short statement of the author’s competence on the topic.
Instructions & scope — who instructed the affidavit, the precise questions to be addressed, and an agreed set of facts the expert is asked to assume. Keep fact assumptions crystal clear; the affidavit must not stray into contesting facts.
Sources & research method — list statutes, leading cases, unreported decisions, government guidance, legal commentaries and databases consulted. For countries with regionally divergent practice, specify whether the opinion covers the whole jurisdiction or a regional part.
Statement of the foreign law — numbered propositions of law (e.g., “Under X jurisdiction, a foreign divorce granted by Y court is recognized when…”) with precise citations to primary sources. Avoid long blocks of narrative — courts appreciate short, citable propositions.
Application to the facts — a reasoned section applying each legal proposition to the facts the court is asked to assume. Distinguish law from assumed facts.
Limits & caveats — identify unsettled points, conflicting authorities or areas of doctrinal doubt. This honesty increases credibility.
Sworn attestation — the attestation paragraph and signature sworn before an authorized officer (notary public or court official) in the foreign jurisdiction.
Exhibits — copies of key cases, statutory extracts and secondary references cited. Number exhibits and cross-reference them in the text.

This structure makes the affidavit accessible to judges, clerks and opposing counsel.

Authentication, legalization and translations — making it admissible in Thailand

Foreign affidavits require proper formalities to be admissible:

Swear/affirm before a competent officer (notary public or court) in the expert’s jurisdiction.
Apostille or consular legalization: if the foreign country is a Hague apostille country, attach the apostille. If not, obtain certification from the foreign ministry and Thai consular legalization where required.
Certified Thai translation: provide an accurate Thai translation of the affidavit and each cited foreign authority. The translator should sign a translator’s declaration; in some registries the translator’s signature must itself be authenticated.
File originals or certified copies with the Thai court or administrative body; keep the authenticated originals available in case the registry demands production.

Check the registry practice in advance — some courts accept scanned copies at an interim stage but insist on originals before final hearing.

Procedural use & likely court treatment in Thailand

Thai courts treat a properly-authenticated affidavit of foreign law as evidence of the foreign law. The court then decides how persuasive that evidence is.
If the opposing party contests the foreign law, the court will usually permit a competing affidavit from another expert. The court may order a joint expert conference, direct additional evidence, or (rarely) arrange testimony by the foreign expert via video link.
Where foreign law is decisive and contested, expect judges to scrutinize primary authorities and translations closely — include full case citations and English (or original language) copies as exhibits to avoid challenge.

Timing, costs and practical planning

Timeline: allow 2–4 weeks for research and drafting for common jurisdictions; allow longer (4–8 weeks) for obscure jurisdictions or complex legal issues. Add time for notarisation, apostille/legalization and Thai translation (another 1–2 weeks).
Costs: variable — a competent foreign practitioner’s draft and sworn affidavit typically ranges from several hundred to several thousand USD (higher for senior experts or urgent work). Legalization, apostilles and translation incur additional fixed fees.
Practical tip: instruct the expert with a concise bundle: agreed facts, key documents, and the court timetable. This avoids repeated drafts and reduces cost.

Risks & common mistakes to avoid

Relying on unsigned opinion letters rather than notarized affidavits — courts may treat them as weaker, hearsay evidence.
Using an expert who cannot be located for cross-examination or who lacks clear credentials.
Failing to legalize or translate the affidavit properly — leading to exclusion or adjournment.
Asking an expert to decide contested facts rather than to assume them — keep the fact/law boundary firm.

Best practice checklist (practical)

☐ Agree the precise questions of foreign law with your client and opposing counsel where possible.
☐ Prepare an agreed statement of facts to be assumed by the expert (so the court hears only legal analysis).
☐ Choose an expert who can swear an affidavit in the foreign jurisdiction and provide a CV and prior work samples.
☐ Ask the expert to provide numbered legal propositions with citations and to attach copies of cited authorities.
☐ Get the affidavit notarized, apostilled or consularized as required.
☐ Commission a certified Thai translation and legalize the translator’s declaration if needed.
☐ File originals/certified copies with the Thai court and serve the opponent with translated copies.
☐ If opponent contests law, be ready to instruct a rebuttal expert or propose a joint expert conference.

Sample short affidavit clause (illustrative)

“I, [name], admitted as a solicitor in [jurisdiction] in [year], of [firm], being duly sworn, say: I have been instructed by [party] to advise on the law of [jurisdiction] on [topic]. My opinion is formed on the documents listed in Annex A, and the facts set out in Annex B are assumed. I have consulted the authorities listed in Annex C. To the best of my knowledge and after the inquiries I describe, I believe the matters contained in this affidavit to be true.”

(Adapt wording to the foreign jurisdiction’s notarial requirements.)

Final practical note

An affidavit of foreign law is the bridge that allows Thai decision-makers to apply non-Thai rules correctly. Invest in a competent, well-credentialed expert; insist on transparent sourcing and authenticated exhibits; and produce a certified Thai translation. Done well, the affidavit shortens hearings and reduces the risk of remittal for further evidence — done badly, it causes delay and can be dispositive against your client.