REQUEST A CONSULTATION

Legal opinion in International law | Cross-border firm decisions

Share

Companies operating in several markets, foreign investors, or even individuals engaged in cross-border relations need legal certainty beyond their own borders. Nowadays, legal decisions are rarely confined to a single country. In this context, the legal opinion in International Law has become a necessity. Drafted by specialized lawyers, it provides a solid and well-founded analysis of legal issues involving different jurisdictions.

Below, we will explain what a legal opinion in International Law is, what its essential features are, how it integrates with domestic law, the relevance of international case law, as well as the firm’s success stories. We have extensive experience in drafting legal reports, supporting both companies and individuals in their decision-making.

A legal opinion in International Law is a legal document that technically analyzes a specific situation with international implications. Its purpose is to offer clients a clear and well-reasoned interpretation of the applicable law, whether it arises from international treaties, multilateral conventions, European regulations, or principles of customary international law.

The opinion may cover anything from international sales transactions to arbitration, including foreign investments and regulatory disputes. It serves as both a risk-prevention tool and a means of support in negotiations or when deciding how to manage a situation.

An international legal opinion differs from a domestic legal opinion in that it is not limited to the laws of a single country. Multiple legal sources come into play here, such as the Vienna Convention on the Law of Treaties, European Union regulations, the case law of the Court of Justice of the EU (CJEU) or the European Court of Human Rights (ECHR), in addition to international arbitration rules.

Therefore, while a domestic opinion focuses on a national legal system, an international legal opinion requires a more complex, multidisciplinary analysis with a global perspective. We invite you to visit our detailed page on legal opinions for more information.

A legal opinion in International Law becomes essential whenever a transaction, contract, decision, or dispute involves multiple jurisdictions, supranational regulations, or public counterparties. Below are some of the most common situations:

International trade and contracts

Companies entering into contracts for international sales, distribution, or agency must ensure that these agreements comply with the laws of all relevant jurisdictions. An international legal opinion helps determine the applicable law and strengthens the company’s position vis-à-vis its partners. It also anticipates risks arising from local regulations or specific regulatory barriers. For instance, in the field of international distribution, a legal opinion may assess whether territorial exclusivity restrictions apply.

International arbitration and cross-border litigation

In international arbitration proceedings or cross-border disputes, both parties and arbitrators often rely on international legal opinions to interpret bilateral investment treaties (BITs), complex contracts, or regulatory frameworks applicable across jurisdictions. An international legal opinion provides technical authority, doctrinal support, and practical expertise. In fact, it can directly influence the final decision of an arbitral or judicial tribunal by clarifying legal issues where uncertainty or divergence exists among legal systems.

Similarly, in the enforcement of foreign judgments (exequatur), a legal opinion may be decisive in demonstrating that a ruling is compatible with the public order of the country where recognition is sought.

Mergers, acquisitions, and foreign investment protection

Legal advice supported by an international legal opinion ensures that a transaction meets the regulatory requirements of each jurisdiction involved. For example, it may determine whether foreign investment restrictions exist in strategic sectors such as energy or telecommunications, or whether the host country imposes specific authorization requirements. It also provides legal certainty against risks such as:

  • Expropriation or nationalization without adequate compensation.
  • Restrictions on transferring capital back to the home country.
  • Disputes with the host state.

This type of legal opinion is important to ensuring the long-term viability and stability of an investment.

International regulatory compliance

Multinational corporations operating in several countries must verify compliance with international regulations such as the EU’s GDPR on data protection, the U.S. FCPA on anti-corruption, or international sanctions imposed by the European Union and the United Nations. A legal opinion in International Law helps design compliance policies and prevent sanctions.

Intellectual property and technology

In projects involving software licensing, patents, or technology transfer on an international scale, it is crucial to determine the applicable law and how copyright or industrial property rights are protected in each jurisdiction.

Maritime and international transport law

Logistics companies, maritime carriers, and airlines frequently face disputes related to international insurance or liability for damaged goods. In these cases, an international legal opinion helps clarify the applicable rules (such as the Brussels Convention, the Montreal Convention, etc.).

International taxation and tax planning

The taxation of cross-border operations is highly complex. A legal opinion may assess double taxation treaties as well as anti-tax avoidance measures, ensuring that companies optimize their tax burden while remaining compliant with the law.

This type of legal opinion requires an in-depth analysis of different jurisdictions, international treaties, case law, and general principles of both public and private international law.

Based on our experience, before issuing a legal opinion we follow a detailed methodology that includes:

  • Identifying the applicable legislation in conflicts of laws.
  • Interpreting international treaties, bilateral and multilateral conventions.
  • Analyzing case law from international courts and arbitral tribunals.
  • Adapting the content of the legal opinion to the needs of each client (companies, individuals, institutions).

What sets us apart?

  • Multidisciplinary perspective: as an international law firm, we combine lawyers specialized in International Law, taxation, commercial, and regulatory matters.
  • Experience across multiple legal systems: our legal opinions are not limited to one country, but integrate different legal frameworks into a coherent analysis.
  • Institutional recognition: an international track record gives greater credibility before courts, arbitral tribunals, and business partners.
  • Risk prevention: we detect potential regulatory obstacles in advance, avoiding issues that could block an investment, contract, or international transaction.

Combining local and international legal expertise makes the difference in safeguarding our clients’ interests. In addition, we have extensive experience issuing legal opinions for companies and drafting legal opinions on European Law, which allows us to complement our knowledge and deliver precise and high-quality reports in international law.

Independence, rigor, and international recognition

In the field of International Law, independence is the cornerstone of trust. Each legal opinion must be impartial, providing a reliable basis for clients to make key decisions. As for methodological rigor, every opinion follows a clear and transparent process: first, presenting the facts; then identifying the applicable rules; next, conducting a comparative analysis of the relevant legal systems; and finally, drawing well-founded conclusions.

The international recognition of our firm lends weight to our legal opinions, giving them credibility and authority before courts, institutions, investors, and business partners.

Global network of partner law firms

We work with a worldwide network of partner firms and local lawyers, allowing us to provide legal insight across different jurisdictions. This ensures that our legal opinions:

  • Are grounded in up-to-date knowledge of local laws and specific regulations.
  • Integrate regulatory, tax, and commercial perspectives unique to each country.
  • Facilitate coordination in multinational operations and cross-border transactions.

Thanks to this global network, we deliver fast, precise, and tailored solutions for our clients — even in emerging markets or on the other side of the world.

Corporate, tax, and regulatory advisory

We stand out by offering comprehensive legal advisory services, covering corporate, tax, and regulatory matters. This approach allows us to:

  • Assess contractual, corporate, and commercial risks.
  • Analyze tax implications under both local and international regulations.
  • Provide advice on compliance, protection, and risk mitigation.

By combining these areas, we bring added value that gives our clients a competitive advantage in the global market.

Experience in International litigation and arbitration

Our team has solid experience in international litigation and arbitration, which enables us to:

  • Accurately assess the viability of our clients’ projects across different legal systems.
  • Draft legal opinions that anticipate potential issues and ensure successful outcomes.
  • Advise on the choice of the most appropriate forum and the drafting of contractual clauses in cross-border contexts.

First, international treaties and conventions are the primary basis of analysis. Their application depends on the year of ratification and entry into force, the States involved that have ratified them, and the subject matter they cover (including their scope or limitations). Treaties are written agreements between two or more States (or international organizations) that assume obligations and commitments under international law, covering areas such as economic matters, free trade, environmental protection, human rights, among others.

Second, where no specific treaties exist, international custom must be examined. This requires demonstrating the existence of two key elements: a continuous and uniform practice, and the recognition of this practice as legally binding (opinio juris). Equally important is the reference to general principles of law, as well as so-called soft law instruments (codes of conduct, guidelines, resolutions). Although not legally binding, they play a relevant role in interpretation.

It is then necessary to explain how these sources interact. For example, jus cogens norms prevail over any other provision, while the principle lex specialis derogat legi generali justifies that a specific rule takes precedence over a more general one. Likewise, when two norms on the same subject contradict each other, the principle lex posterior derogat priori applies, meaning the later rule always overrides the earlier one. The analysis within an international legal opinion must also address the relationship between International Law and the domestic law of each State. In practice, many legal disputes arise precisely from how international norms are —or are not— applied within national legal systems.

For this reason, the interpretation of international treaties must follow the guidelines set out in Articles 31 to 33 of the Vienna Convention on the Law of Treaties. These provisions establish that treaties must be interpreted in good faith, considering their context and the object and purpose they pursue. This approach allows for a clear explanation of how to act in a specific case, what legal consequences may follow, and anticipating the outcomes that courts, authorities, or counterparties might adopt.

International Case Law and Relevant Tribunals (ICJ, ECHR, Arbitration)

An international legal opinion is not built solely on written norms — it must also rely on the case law of relevant courts and tribunals, which provide authority to the reasoning.

The International Court of Justice (ICJ) is the principal judicial organ of the United Nations. While its judgments are binding only on the parties to the dispute, its reasoning carries significant weight within the international community. A legal opinion should identify comparable decisions, explain the ratio decidendi, and clarify why they are applicable or, alternatively, which differences might lead to a different outcome.

The European Court of Human Rights (ECHR) also plays a role when the States concerned have ratified the European Convention on Human Rights. In this context, a legal opinion must analyze how the Court interprets the margin of appreciation granted to States, how it applies the proportionality test, and how it addresses positive and negative obligations.

In the economic sphere, international arbitration has become the most common mechanism for resolving transnational disputes (through institutions such as ICSID or the ICC). Although arbitral awards do not create binding precedent, the consistent repetition of principles provides practical guidance. Furthermore, the effectiveness of an award depends on its enforcement under the 1958 New York Convention.

Ultimately, the value of case law lies in selecting the most recent and doctrinally consolidated decisions from authoritative forums, ensuring both credibility and practical relevance.

legal opinion international law international court of justice

Below, we examine the main benefits of a legal opinion in International Law:

One of the key advantages of an international legal opinion is its ability to identify and minimize legal risks before a decision is made. A preventive international legal opinion makes it possible to:

  • Detect potential conflicts of laws between jurisdictions.
  • Avoid contractual clauses that could be null or unenforceable in certain countries.
  • Anticipate issues that could lead to economic or administrative sanctions in a given jurisdiction.

Improved decision-making

A legal opinion in International Law brings clarity. Individuals and companies alike can base their decisions on objective information, assessing the feasibility of international projects or optimizing decisions in specific contexts (for example, in a cross-border inheritance). Not only does it enhance decision-making, but it also allows negotiations to be conducted from a stronger position.

Individuals and businesses operating internationally must be aware of the risks they assume when acting without specialized legal advice.

Regulatory non-compliance and sanctions

Lack of knowledge or misinterpretation of international and local regulations can result in compliance failures that trigger sanctions. The most common risks include:

  • Fines and penalties imposed by national or international authorities.
  • Contracts declared null and void due to clauses that do not comply with applicable law.
  • Civil or administrative liability.

Without an international legal opinion, exposure to legal and financial sanctions increases significantly.

Loss of opportunities and poor decision-making

Failing to obtain a preventive legal opinion can lead to poor decisions that compromise the success of a case or project, such as:

  • Rejection by investors or partners who require a minimum level of legal certainty before committing.
  • Missed business opportunities due to a lack of analysis of foreign regulatory frameworks.
  • Difficulty accessing international markets because of unanticipated legal risks.

Below, we share several success cases where well-founded legal opinions prepared by our team helped clients achieve their goals:

Opinion on International sales contracts

A Spanish client in the industrial sector was about to sign an international sales contract with a Brazilian company for the supply of machinery. Before closing the deal, they requested an international legal opinion from us to assess the legal security of the contract. Our opinion analyzed:

  • The contract’s compatibility with the Vienna Convention (CISG).
  • The validity of the arbitration clause submitted to the ICC.
  • Potential trade barriers and applicable international sanctions.

✅ Result: The client signed with full confidence, incorporating contractual adjustments in their favor and securing commercial success in Brazil.

Protection of foreign investments

A German fund planned to invest €50 million in renewable energy projects in Morocco. Before committing the capital, they contacted us for an international legal opinion aimed at protecting their investment. Our report included:

  • An assessment of bilateral treaties with Morocco.
  • Guarantees against expropriation and fair treatment clauses.
  • Access to arbitration in case of disputes.
  • Tax and regulatory recommendations.

✅ Result: The fund finalized the joint venture with clauses that protected its investment and reduced the risk of arbitrary measures by the host State.

Disputes between states and private companies

A U.S. technology company was sanctioned in Africa with the suspension of its licenses. The company requested an international legal opinion to evaluate possible defense strategies (U.S.–Africa). Our analysis determined:

  • That the measure amounted to expropriation in violation of a free trade agreement.
  • The procedural options, including access to international arbitration under the New York Convention.
  • Potential negotiation strategies.

✅ Result: The company successfully negotiated an agreement with the African State, resuming operations without the need to pursue arbitration.

Compliance and International sanctions

A European multinational in the financial sector sought to expand operations into the Middle East, but faced risks related to international sanctions and regulatory uncertainties. They requested an international legal opinion to assess their expansion. Our opinion included:

  • A review of the regulations in the relevant States governing financial transactions.
  • Identification of risks and sanctioned countries.
  • Recommendations to implement an international compliance program tailored to their business.

✅ Result: The company successfully launched operations in three countries in the region without regulatory incidents.

Due Diligence and regulatory compliance

A Portuguese company in the chemical sector wanted to acquire a business in Asia and requested a legal opinion before signing the agreement. Our opinion included:

  • A review of local legal obligations, including licenses and permits.
  • An assessment of contracts that could affect the transaction.

✅ Result: The client completed the acquisition with protective clauses integrated, ensuring a secure integration process.

A legal opinion in International Law is a legal report prepared by a lawyer specialized in international norms, treaties, and case law. Its purpose is to clarify the application of International Law or how rules from different States interact in a specific case, and to provide legal certainty in international settings.

Law firms with experience in both Public and Private International Law, used to working with treaties, customary international law, case law (ICJ, ECtHR, arbitrations), and the interaction of national laws. It is advisable that the opinion be issued by a law firm with cross-border practice, as this provides greater credibility in international forums.

The process follows a structured method:

  • Presentation of the relevant facts.
  • Identification of applicable norms (treaties, custom, general principles).
  • Analysis of case law from international courts and arbitral tribunals.
  • Assessment of domestic law in relation to international law.
  • Clear and applicable conclusions for the client’s case.

4. How to prioritize between a treaty and customary international law?

In principle, a treaty prevails among the parties that have ratified it. However, when there is a jus cogens norm or subsequent customary practice, the rules of lex specialis (special rule over general) or lex posterior (later rule over earlier) must be applied.

5. Is ICJ case law binding on third States?

It is not binding on those who are not parties to the dispute. Nevertheless, the judgments of the International Court of Justice carry great weight and often influence other international courts, arbitrators, and institutions, setting legal standards.

6. Which carries more weight in the ECtHR: proportionality or the margin of appreciation?

The proportionality test has stronger force when the right at stake is essential (life, liberty, non-discrimination). The margin of appreciation of States gains importance in areas more closely linked to culture or political decisions of States. A specific assessment is required in each case.

An opinion becomes a negotiation advantage because it:

  • Outlines possible settlement scenarios.
  • Strengthens credibility vis-à-vis the counterparty.
  • Anticipates the arguments and objections of the other side and allows preparation of responses.
  • Facilitates agreement on the forum or arbitral seat.

A domestic report analyzes the laws of a specific country. An international legal opinion, by contrast, integrates the laws of several States, multilateral treaties, and international case law, providing a comparative and cross-border perspective.

  • International contracts for sale of goods or joint ventures.
  • Foreign investments.
  • Conflicts of law between States.
  • Claims before the ECtHR or the ICJ.
  • Issues relating to the protection of fundamental rights.

The main advantage is credibility. An internationally recognized law firm not only provides rigorous legal analysis but also legitimacy before courts, arbitrators, institutions, and business partners. In addition, it ensures a multidisciplinary assessment that covers different areas of law.

Yes. Although it does not replace the judgment of the court or arbitrator, an international legal opinion provides authority and is often presented as expert evidence or a reference document. Its weight depends on the soundness of the analysis and the reputation of the issuing lawyer or firm.

Public International Law governs relations between States, treaties, human rights, or investment arbitration. Private International Law, on the other hand, resolves conflicts of laws and jurisdictions between individuals and companies in international transactions. A legal opinion may cover one or both areas, depending on the case.

Yes. Anticipating how international norms (such as economic sanctions, export controls, or environmental regulations) apply enables companies and individuals to adapt their contracts and decisions, thereby avoiding sanctions, financial penalties, or even trade blockages.

Secure your decisions in international cases

Making decisions in scenarios where multiple States, national laws, and international law converge is never simple. Such situations carry risks that must be anticipated through expert analysis.

At Arthur & Marin, we transform complexity into confidence: we have a team of lawyers specialized in international legal opinions, with experience across multiple jurisdictions, proficiency in several languages, and a global network of contacts. This allows us to provide not only legal certainty but also real competitive advantages.

Contact us today at info@arthurmarin.com or call +32 465 345 345.

💡Take the first step toward solid and precise international advice. Turn legal uncertainty into an opportunity to grow with confidence.

Latest posts

we talk?

Let´s work together

Linkedin-in Twitter Instagram

Contact us

info@arthurmarin.com

Call us

+32 465 34 53 45

Scroll to Top