Affidavit of Foreign Law

Affidavit of Foreign Law . When a court or tribunal must apply a foreign legal rule, that rule is typically treated as a question of fact rather than law; the party relying on it must prove what the foreign law says and how it applies. An affidavit of foreign law (sometimes called a legal-opinion affidavit) and the reciprocal affidavit of Thai law are the practical instruments lawyers use to do that proving. This guide explains their purpose, who prepares them, how they are drafted and authenticated, how courts and arbitral tribunals treat them, practical drafting tips, and a step-by-step checklist for getting them admitted and relied upon.

Purpose and when they are needed

Affidavit of foreign law: Used in litigation or arbitration when a forum (court or tribunal) must determine how the law of another jurisdiction governs a matter in dispute — for example, whether a foreign contract-formation rule applies, what the test for validity is under another country’s company law, or whether a foreign tax statute creates an obligation. Because foreign law is a fact to the domestic forum, an affidavit (or expert legal opinion served as an affidavit) tells the court what that foreign law is and how it should be applied to the facts.
Affidavit of Thai law: Used in foreign proceedings when a foreign court or arbitral tribunal must know how Thai law treats an issue (e.g., land title rules, company law, succession, or procedural questions). It may also be used internally where a clear, signed statement of Thai legal position is helpful to the record.

Both documents function as evidence — they are not binding law by themselves. The issuing lawyer’s reasoning and authorities assist the factfinder, which in turn decides what weight to attach.

Who should prepare the affidavit

Qualified counsel or academic experts in the relevant jurisdiction: the person preparing the affidavit should be demonstrably competent in the law being opined on. For an affidavit of foreign law used in Thailand, a Thai-qualified lawyer or academic with expertise in the area is ideal; for an affidavit of Thai law used abroad, a Thai advocate with relevant experience or a Thai law academic is suitable.
Content experts where necessary: for technical regulatory, tax or specialized corporate law questions, joint production with subject-matter experts (and clear statements of the limits of the legal opinion) improves credibility.

The affidavit should begin by identifying the affiant, their qualifications, and the basis for their expertise (degrees, practice experience, publications, regulatory roles).

Typical structure and essential contents

Caption and identification — case name, court/tribunal, parties, and a clear title (“Affidavit of [Name] on the Law of [Jurisdiction]”).
Qualifications and instructions — a signed statement of the affiant’s qualifications, confirming they were instructed by (identify counsel) and stating documents provided and assumptions made.
Scope and issues — a concise list of the legal questions the affidavit addresses (e.g., “Whether X statute creates a floating charge on assets”).
Statement of law — clear exposition of the relevant statutory provisions, leading cases, and accepted secondary sources in the foreign jurisdiction. Quote material statutory language and summarize leading authorities with citations.
Application to facts — reasoned application of the foreign law to the specific factual matrix of the dispute; include caveats where facts are assumed.
Conclusions / opinion(s) — numbered, clear conclusions answering the posed questions.
Appendix of authorities — full copies or certified extracts of statutes, cases and international instruments relied upon.
Declaration of truth — the formal affidavit clause (“I solemnly declare…”) with date and signature block.
Authentication — notarization, and where required for overseas use, consular legalization or apostille, plus certified translation if the receiving forum requires a language other than the affidavit’s original.

Authentication, legalization and translation

Notarization: most courts expect the affiant’s signature to be notarized.
Apostille or consular legalization: check the receiving jurisdiction’s rules. If the receiving state is party to the Hague Apostille Convention and the affidavit is notarized in an apostille state, an apostille may be sufficient. Where apostilles are not accepted (for example, when Thailand is a party but another state is not, or vice versa) consular legalization may be required. Always confirm whether the forum requires further legalization by the Ministry of Foreign Affairs of the affiant’s country or by the embassy of the forum state.
Certified translation: submit an official translation with a translator’s certification and—if required—notarization and legalization of the translation.

Evidentiary weight and cross-examination

Evidentiary weight: an affidavit of law is persuasive; tribunals evaluate it alongside other evidence. A well-reasoned affidavit that cites authoritative primary sources (statutes, published judgments, official commentary) carries significant weight.
Opposing proof: the opposing party may file a rebutting affidavit or call the affiant as a witness. Courts sometimes treat differing expert opinions as a matter for cross-examination or for determination by the court based on which opinion is better reasoned and supported.
Cross-examination (viva voce evidence): in some civil-law systems or arbitration rules, oral expert testimony and cross-examination are available; in other systems the dispute is decided on written submissions. If the affiant may be called for cross-examination, the affidavit should anticipate likely lines of attack and explain methodology and sources.

Use in arbitration and international proceedings

Arbitral tribunals commonly accept legal-opinion affidavits. Advantages in arbitration include flexibility on format, a generally receptive audience for expert legal reasoning, and the tribunal’s power to weigh competing expert views. Ensure the arbitration rules (ICC, SIAC, HKIAC, etc.) permit expert evidence and follow any procedural directives about disclosure, witness statements and availability for hearing.

Practical drafting tips (do’s and don’ts)

Do:

Identify the affiant’s credentials fully and transparently.
Set out the precise legal question(s) and any factual assumptions.
Rely on primary authorities first (statutes, reported decisions), supported by reputable secondary sources.
Attach certified copies of cited authorities, properly paginated and indexed.
State limitations and alternative views candidly; courts respect balanced opinions.

Don’t:

Overreach by giving opinions on facts outside the affiant’s competence.
Fail to state applicable conflicts of law or divergence in authority among jurisdictions.
Skip authentication or translation steps required by the receiving forum.

Practical checklist before filing

Confirm which law the forum treats as foreign and whether judicial notice applies.
Select a qualified affiant and obtain written instructions and full factual materials.
Prepare a tight issue list and sourcing plan (statutes, cases, commentary).
Draft the affidavit with an appendix of full authorities and local citations.
Notarize the affidavit; obtain apostille or consular legalization where needed.
Have translations certified and notarized.
Serve within the timetable set by procedural rules and be prepared for rebuttal or oral testimony.

Conclusion

Affidavits of foreign law and affidavits of Thai law are technical, evidentiary tools that transform questions of foreign law from abstract queries into concrete, adjudicable facts. Their persuasive power rests on the affiant’s credentials, the clarity of reasoning, the use of primary authorities, and careful adherence to authentication and translation formalities. For cross-border litigation or arbitration, early planning — selecting the right affiant, assembling complete source materials, and anticipating rebuttal — sharply increases the chance that a tribunal will accept and apply the foreign-law conclusions you advance.