International Law in Seven Topics

Why study international law now

For a long time, international law was treated in Brazil as a distant subject, worth only a few questions on the bar exam and civil-service examinations. In 2026 it is in the news every day: wars that test the rules of the UN Charter, the selection of a new Secretary-General, a historic trade agreement between Mercosur and the European Union in force since May.

It is also part of ordinary people's lives. Families with members abroad, companies that import and export, Brazilians who inherit assets outside the country or divorce foreign nationals all depend on treaties, conventions and international cooperation procedures.

This article covers the seven topics that appear most often in exams — and shows, at the end, how they translate into practical situations.

1. Treaties: from handshake to Official Gazette

A treaty is a formal agreement concluded between subjects of international law — States and international organizations — governed by international law and intended to produce legal effects. The core instrument is the Vienna Convention on the Law of Treaties (1969), promulgated in Brazil by Decree 7,030/2009, which enshrines the principle of pacta sunt servanda and prohibits a State from invoking its domestic law to justify failure to perform a treaty (Art. 27).

How a treaty becomes part of Brazilian law:

1. Negotiation — conducted by the Executive, through diplomacy.
2. Signature — signals political intent, but does not yet fully bind the State.
3. Approval by Congress — through a legislative decree, under Article 49, I, of the Constitution.
4. Ratification — an act of the President (Art. 84, VIII) confirming Brazil's consent at the international level.
5. Promulgation and publication — by presidential decree, which makes the treaty enforceable domestically.

A current example: the Mercosur–European Union Interim Trade Agreement was approved by Legislative Decree 14, published on March 17, 2026; Brazil notified the European Commission on March 18, and the agreement entered into provisional force on May 1, 2026.

Hierarchy in Brazilian law. A treaty's rank depends on its content and on the procedure followed:

Exam trap: signing is not incorporating. And Congress does not "ratify" treaties — it approves them; ratification is the President's act.

2. The UN: who recommends, who decides, who judges

General Assembly vs. Security Council. The General Assembly brings together all 193 member States, each with one vote. It decides by simple majority and, on important questions, by two-thirds (Art. 18 of the Charter). Its resolutions are, as a rule, recommendations: they carry political and diplomatic weight, but do not create general obligations as a treaty does. The Security Council has 15 members — 5 permanent members with veto power (United States, Russia, China, France and the United Kingdom) and 10 elected for two-year terms — and may adopt binding measures under Chapter VII of the Charter: sanctions, embargoes, peacekeeping missions and authorization of the use of force.

A current fact: the selection of a successor to António Guterres, whose term ends on December 31, 2026, illustrates the division of roles. The Security Council held its first informal straw poll on July 30 and must recommend a name; the General Assembly makes the formal appointment, and the new Secretary-General takes office on January 1, 2027. The candidates include Rafael Grossi, Michelle Bachelet and Rebeca Grynspan — which may, for the first time, bring a woman to the post.

International Court of Justice vs. International Criminal Court.

Exam traps: individuals and companies cannot bring cases directly before the ICJ; without the State's consent there is no contentious judgment; and the ICJ and the ICC are both in The Hague, but are not the same. Brazil recognizes the jurisdiction of the ICC (Art. 5, § 4, of the Constitution).

3. Diplomatic relations: immunity is not impunity

The Vienna Convention on Diplomatic Relations (1961), promulgated in Brazil by Decree 56,435/1965, is the basis of diplomatic missions. Their functions are to represent the sending State, protect its interests and those of its nationals, negotiate with the receiving State, ascertain conditions locally and promote friendly relations.

Privileges and immunities — what exams ask:

• Inviolability of the mission (Art. 22): agents of the receiving State may not enter without the consent of the head of mission, and the receiving State must protect it.
• Personal inviolability of the agent (Art. 29): a diplomat may not be arrested or detained.
• Immunity from jurisdiction (Art. 31): absolute in criminal matters; in civil and administrative matters there are exceptions, such as actions concerning private real estate, succession and private commercial activity.
• Waiver (Art. 32): only the sending State may waive immunity, and it must do so expressly.
• Persona non grata (Art. 9): the receiving State may declare a diplomat unwelcome at any time, without giving reasons; the sending State must recall the person.

The logic is functional: immunity protects the international function, not the person. The diplomat remains bound to respect local laws and not to interfere in internal affairs. Consular relations follow a different treaty — the 1963 Vienna Convention — with narrower immunities, limited to official acts.

Immunity of the foreign State itself. Brazilian case law distinguishes acts jure imperii (performed as a sovereign, immune) from acts jure gestionis (such as hiring local employees), for which the foreign State may be sued — although enforcement against its assets remains, as a rule, protected.

4. The Holy See: a subject sui generis

The Holy See is a subject of international law and is distinct from the Vatican City State. The Holy See is the spiritual and juridical authority of the Catholic Church, which acted internationally long before 1929; the Vatican is the territorial base created by the Lateran Treaties, signed that year with Italy, to guarantee its independence.

It is the Holy See that concludes treaties — concordats — maintains diplomatic relations through apostolic nuncios and takes part in international bodies, including as a permanent observer at the UN. In Brazil, the 2008 Brazil–Holy See Agreement, promulgated by Decree 7,107/2010, deals with the legal status of the Catholic Church in the country and was examined by the Supreme Federal Court in its judgment on religious education in public schools (ADI 4,439).

Exam trap: stating that the Vatican is the main subject sinks the answer. International legal personality belongs to the Holy See.

5. The Geneva Conventions: even war has rules

International humanitarian law (IHL) does not address whether a war is lawful — that is jus ad bellum, governed by the UN Charter. IHL regulates how war must be conducted (jus in bello) and applies equally to all parties, regardless of who started the conflict.

The four Conventions of 1949:

1. Wounded and sick members of armed forces in the field (land).
2. Wounded, sick and shipwrecked members of armed forces at sea.
3. Prisoners of war.
4. Protection of civilians in time of war.

Common Article 3 of the four Conventions extends minimum guarantees to non-international armed conflicts — humane treatment and the prohibition of torture, summary executions and hostage-taking.

Additional Protocols: those of 1977 expanded protection in international conflicts (Protocol I) and non-international conflicts (Protocol II); the 2005 Protocol (Protocol III) created the red crystal emblem, alongside the red cross and red crescent.

Practical principles: distinction between combatants and civilians; proportionality of attacks; precaution; prohibition of attacks on hospitals and medical personnel; humane treatment of prisoners. Grave breaches constitute war crimes, which may be tried by national courts or by the ICC.

Why it matters in 2026: the conflicts in the Middle East and Ukraine put these principles to the test every day — attacks on civilian infrastructure, hospitals and shipping lanes are assessed in light of IHL.

6. International trade: not a lawless land

The World Trade Organization (WTO), created in 1995 by the Marrakesh Agreement, administers the multilateral trade agreements, serves as a negotiating forum and settles disputes among its members.

Key principles: non-discrimination — in the twin senses of most-favored-nation treatment (GATT Art. I) and national treatment (Art. III); reciprocity; predictability, through bound tariffs; and fair competition.

Barriers: tariff barriers, which are import duties; and non-tariff barriers, such as quotas, licenses and technical or sanitary requirements.

Dumping: exporting at a price below the normal value in the home market. Once injury to the domestic industry is proven, the importing country may impose anti-dumping duties. In Brazil, the procedure is governed by Decree 8,058/2013.

Dispute settlement in crisis. The WTO Appellate Body has been paralyzed since December 2019, because the United States has blocked the appointment of new members. In practice, the party that loses at first instance can appeal "into the void" and prevent a final decision — one of the signs of the crisis of trade multilateralism, worsened by the unilateral tariffs of recent years.

Regional agreements: Mercosur. Created by the Treaty of Asunción (1991), with international legal personality conferred by the Protocol of Ouro Preto (1994), Mercosur is an imperfect customs union, with a Common External Tariff and exceptions. Its most recent milestone is the Interim Trade Agreement with the European Union, in force since May 1, 2026, which is still under review by the Court of Justice of the European Union for its definitive entry into force.

7. From the textbook to real life: international law for individuals and businesses

The same treaties that appear in exams solve concrete problems for families and businesses with ties outside Brazil.

In all these cases, advance planning avoids the worst scenario: two proceedings in two countries, with double the cost and conflicting decisions.

Exam traps, in brief

• Signature does not incorporate a treaty; Congress approves, and the President ratifies and promulgates.
• A General Assembly resolution recommends; the Security Council may decide with binding force (Chapter VII).
• The ICJ judges States; the ICC judges individuals.
• Diplomatic immunity is not impunity, and only the sending State can waive it.
• The subject of international law is the Holy See, not the Vatican.
• The Geneva Conventions do not say whether war may be waged, but how it must be limited.
• A human rights treaty has the rank of a constitutional amendment only if approved under the procedure of Art. 5, § 3; otherwise, it is supra-legal.

Andrade & Cintra Advogados, through its international division, Sintra Legal & Partners, handles Brazil–United States matters involving succession, family, contracts and investments. This text is for information only and does not replace an individual analysis of each situation.

Sources

• Acordo provisório Mercosul–UE entrará em vigor em 1º de maio, diz governo — Band, March 25, 2026 (in Portuguese)
• Entrada em vigor do Acordo Provisório de Comércio Mercosul–União Europeia — Ministry of Agriculture and Livestock/LegisWeb (in Portuguese)
• ONU começa votação para definir próximo secretário-geral — Revista Oeste (in Portuguese)
• Começa a corrida para encontrar o próximo secretário-geral da ONU — UNRIC (in Portuguese)
• Em crise, contestada e sob pressão, ONU elege novo secretário-geral — Metrópoles, August 3, 2026 (in Portuguese)
• Charter of the United Nations (1945) and Statute of the International Court of Justice
• Vienna Convention on the Law of Treaties (1969) — Decree 7,030/2009
• Vienna Convention on Diplomatic Relations (1961) — Decree 56,435/1965
• Geneva Conventions (1949) and Additional Protocols (1977 and 2005)
• Brazil–Holy See Agreement (2008) — Decree 7,107/2010
• Starting material: the "7 assuntos de Direito Internacional" carousel, Nêuron Aprendizado Inteligente (@neuronappoficial)

Informational content. It does not constitute legal advice and does not create an attorney-client relationship. Matters under U.S. law are handled by attorneys licensed in the relevant jurisdiction.