Affidavit of Foreign Law

When a Thai court, administrative body or arbitral tribunal must apply foreign substantive or procedural rules, an affidavit of foreign law is the conventional, often decisive method for proving what that law is. It is expert evidence: it tells the decision-maker what the foreign law is and how it operates, not what facts occurred. Getting this document right speeds hearings, reduces costly rebuttals and avoids entirely predictable procedural rulings that delay your case. This guide is a practitioner’s playbook — structure, authorship, authentication, exhibits, tactical uses, costs, timelines and common traps.

What an affidavit of foreign law does (and when you need one)

A Thai decision-maker needs to know foreign law in situations such as:

• Whether a foreign judgment or insolvency ruling should be recognized or given effect;

• The legal consequences of foreign corporate acts (e.g., whether a foreign registry entry is conclusive);

• Foreign family-law questions (marriage/divorce validity abroad);

• Issues of foreign procedure (service, limitation periods) that affect Thai proceedings or enforcement;

• Choice-of-law disputes where the foreign legal rule will determine the outcome.

The affidavit establishes the content and application of that foreign law; if contested, the court will allow rebuttal affidavits or order expert testimony.

Who should prepare it — credibility and availability

Pick someone who can be produced for questioning and whose credentials are straightforward to verify:

• A practicing foreign lawyer admitted in the target jurisdiction — best for courts’ practical application and current case law.

• A specialist academic with peer-reviewed work — useful for doctrinal or historical explanations.

The affiant must set out credentials (admission year, firm/university, notable cases or publications), the scope of their practice, and a statement of availability to attend for cross-examination (video attendance is normally acceptable). Judges value authors who can be tested in court.

Clear structure — what judges and clerks want to see

A cramped, discursive affidavit wastes time and invites rebuttal. Use a numbered, modular format:

1. Caption & instruction: who instructed the expert and the precise legal questions asked.

2. Qualifications: short CV and statement of competence.

3. Assumed facts (Annex A): a numbered list of facts the expert is told to assume. The affidavit must assume facts — not try to prove contested factual matters.

4. Legal propositions: short numbered statements of the foreign law (e.g., “Proposition 1: Under X law, a foreign registry is conclusive except where fraud is shown”), each with pinpoint citations.

5. Application to assumed facts: reasoned application, cross-referencing the numbered propositions and assumed facts.

6. Sources & method: databases searched, last search date, and whether unreported decisions were obtained directly.

7. Exhibits: full texts of statutes and full judgments relied on (with certified translations).

8. Caveats: identify significant conflicting authorities and explain weight.

9. Attestation: sworn statement and notarial block.

Number every paragraph and exhibit; include a short exhibit map linking propositions to supporting authorities.

Authentication, legalization & translation — do these steps early

For submission in Thailand you must do authentication correctly or a hearing will be adjourned:

1. Swear the affidavit before a competent officer in the foreign jurisdiction (notary/court officer).

2. Apostille the notarial signature if the foreign country is a Hague member; consular legalization (foreign ministry + Thai consulate) if it is not. This proves the notary’s authority.

3. Certified Thai translations of the affidavit and every primary authority cited. The translator should sign a declaration of accuracy. Some courts require legalization of the translator’s signature; check procedural rules.

4. File originals or certified copies as the tribunal requires and retain apostilled originals for inspection.

Do not postpone apostille or translation: these steps often add 1–3 weeks.

Exhibits — attach full primary materials

Attach the entire statute texts and entire judgments relied upon — not excerpts or headnotes only. For unreported or regional decisions include full judgments and identify territorial scope where laws vary regionally (states/provinces). Courts dislike cherry-picked snippets; give the judge the full authorities so they can test the reasoning.

Tactical deployment — when and how to use an affidavit

• File early where foreign law is dispositive (recognition, limitation, incapacity) to avoid wasted hearing time.

• Budget for rebuttal: opposing parties commonly file one rebuttal affidavit; plan for it.

• Joint expert or neutral court-appointed expert: propose a single neutral statement of law to save time and costs where practical.

• Availability for oral examination: instruct the expert to be available for the hearing or to attend by video. Courts often require the expert to answer questions if the law is contested.

If foreign law is central, lock down the expert and start legalization well before the hearing date.

Practical drafting tips that reduce disputes

• Use short numbered legal propositions (judges like bite-size, citable statements).

• State the research cut-off date explicitly.

• Where law is unsettled, identify the competing lines and explain why you prefer one. Judges respect candor.

• Keep fact assumptions separate; never try to have the expert prove contested facts.

• Request the expert preserve working notes and search logs (the court may inspect in cross-examination).

Timeline & cost expectations (practical)

• Authoring & research: 1–3 weeks for common jurisdictions. Complex comparative topics take longer.

• Notarization + apostille/legalization: 3–14 business days depending on country and consulate workload.

• Translation: 2–7 business days depending on volume.

• Costs: from a few hundred USD (simple affidavit) to several thousand USD for senior counsel, rush work, extensive research, translations and legalisation. Always budget for a rebuttal affidavit and potential expert attendance.

Start early — legalization time is the frequent bottleneck.

Common pitfalls (and how to avoid them)

• Unsigned opinion letters instead of sworn, apostilled affidavits — weaker and sometimes inadmissible. Use sworn, legalized documents.

• Poor translations that misstate law — use certified legal translators experienced in the source jurisdiction.

• Blurring law and fact — the expert must assume facts; do not ask them to decide contested factual questions.

• Unavailable expert — secure a written undertaking that the expert will attend (video) if required.

Run a short pre-execution checklist to prevent these mistakes.

Model short affidavit clause (ready to adapt)

“I, [Name], admitted as an advocate and 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 the following questions: (1) [Precise question 1]; (2) [Precise question 2]. The facts set out in Annex A are assumed. My opinion is based on the documents listed in Annex B. Attached as Exhibits 1–N are the primary authorities relied upon. To the best of my knowledge and after the inquiries I describe, the matters herein are true.”

Annex A = assumed facts; Annex B = documents consulted.

Ready checklist — what to do now

1. Agree precise legal questions with counsel.

2. Prepare an agreed facts Annex A or ask the court to fix assumed facts.

3. Instruct a credentialed foreign lawyer/academic and confirm availability.

4. Set research cut-off date and request a search statement.

5. Arrange notarization and apostille/consular legalization early.

6. Order certified Thai translations of affidavit and exhibits.

7. File per tribunal rules and retain originals and apostilles.

Final practical note

An affidavit of foreign law is a specialist deliverable: treat it like an expert report — choose a credible author, define precise legal questions, attach full primary authorities, authenticate and translate everything correctly, and budget for rebuttal and possible oral testimony.