International Law: Treaties and Customs
Item 7: The Usual
Concept and Training of International Custom
Customary international law, as per Article 38.1b of the Statute of the International Court of Justice, arises from practice accepted as law by states. This spontaneous process results from a practice based on the belief that it entails a legal obligation.
Two mandatory aspects define international custom: a material aspect (the will of states, composed of three elements) and a spiritual aspect (opinio juris).
Elements for the Formation of Custom
Judge De Castro identified four essential elements for the existence of custom:
General Practice
Practice must be carried out by a representative number of states. Once consolidated, it binds all states (except persistent objectors).
Constant and Uniform Practice
Practice should be common among states. While not identical, behaviors must largely coincide, with similar solutions for similar situations. States acting contrary to established practice are considered persistent objectors.
Lasting Practice
While historically requiring extended periods (e.g., 100 years), the duration for establishing custom has significantly decreased due to rapid scientific, technological, and social advancements. International organizations like the United Nations accelerate this process.
Opinio Juris (Spiritual Element)
This crucial element represents states’ belief that their practice involves a legal obligation. Proving opinio juris can be challenging, often relying on unilateral acts, case law, domestic law, and resolutions of international organizations.
Kinds of Customs
Customs are categorized as:
Universal
Binding on all states except persistent objectors.
Particular
Applying to a smaller number of states, further divided into:
Regional
Applying to states with shared characteristics (historical, economic, geographical).
Local
Applying to a very small area, sometimes only two states.
Enforceability Against Habit
Persistent Objector
A state unequivocally opposing a forming custom. This status is not recognized once the custom is established.
Burden of Proof of Habit
For universal customs, the objecting state must prove its persistent objection during the custom’s formation. States formed after the custom’s crystallization have a short period to decide.
For particular customs (regional or local), the burden of proof lies with the state claiming the custom.
Topic 8: The Treaties
Concept and Function of the Treaty
The legal regime of international treaties is governed by two conventions: the 1969 Vienna Convention on the Law of Treaties and the 1986 Vienna Convention on the Law of Treaties between States and International Organizations. Both are largely identical, with the latter incorporating international organizations.
A treaty is a written international agreement between states, between states and international organizations, or between international organizations, governed by international law, whether in a single or multiple instruments, regardless of its specific designation.
Five key elements define a treaty:
Written Agreement
Treaties must be in writing to create binding obligations.
Single or Multiple Instruments
Treaties can be established in one or several texts.
Any Designation
The term “treaty” encompasses various names like convention, agreement, pact, statute, etc.
Agreement Between Subjects of International Law
This includes states and international organizations. All states have treaty-making capacity (Article 6, 1969 Vienna Convention). Capacity for international organizations depends on their internal regulations.
Governed by International Law
Treaties are governed by international law, not internal state regulations.
Classification of Treaties
By Number of States:
Bilateral
Between two states.
Plurilateral
Between more than two states, but not a significant number.
Multilateral
Between a large number of states, further classified as:
Open
Allowing non-members of the adopting international organization to join.
Closed
Limited to members of the adopting international organization.
By Object and Purpose:
Contracts
Regulating exchange of services based on reciprocity.
Normative Treaties
Often lacking reciprocity, with states assuming obligations towards individuals within their jurisdiction.
Conclusion and Entry into Force of Treaties
Two stages: treaty development and adoption, and integration into domestic law.
First Stage
Three phases: negotiation, adoption, and authentication.
Negotiation
Conducted by representatives with full powers (Article 2.1c, 1969 Vienna Convention). Presumption of capacity exists for representatives in international organizations or conferences (Heads of State, government, foreign ministers, diplomatic mission heads). In Spain, the Council of Ministers decides on treaty negotiation, with the Minister of Foreign Affairs leading the process.
Adoption
Occurs when states reach an agreement. Within international organizations, adoption typically requires a two-thirds majority (Article 9.2, 1969 Convention).
Authentication
States certify the text’s correctness and finality. Subsequent amendments are limited to error correction with all parties’ consent.
Signature
Signature alone doesn’t bind a state; ratification is required.
Second Stage
States express consent to be bound, often through signature and ratification. Spanish law requires parliamentary approval (Organic Law) and ratification by the Minister of Foreign Affairs on behalf of Spain, with the instrument signed by the Head of State (King).
Treaty validity often depends on a clause specifying a minimum number of ratifications or a timeframe.
Basic Principles of the Law of Treaties
Pacta Sunt Servanda, Rebus Sic Stantibus
Pacta sunt servanda (Article 26, 1969 Vienna Convention) mandates states’ good faith compliance with treaties. Article 27 prohibits invoking domestic law to justify non-compliance.
Rebus sic stantibus allows withdrawal due to changed circumstances or serious irregularities in domestic integration, unless the treaty establishes a border or the change results from the state’s violation of an international obligation.
Ex Vinculum Advenit Consensus
A state’s written expression of consent to be bound. Spanish Constitution (Articles 93 and 94) requires parliamentary approval, requested by the Council of Ministers, followed by ratification by the Minister of Foreign Affairs and signature by the King.
Reserves
Unilateral statements (Article 2.1d, 1969 Vienna Convention) made by a state upon signing, ratifying, accepting, approving, or acceding to a treaty, to exclude or modify the legal effect of certain provisions in their application to that state.
Key elements:
Unilateral Declaration
Accompanying the state’s consent (Article 19, 1969 Convention), unless prohibited by the treaty, limited by the treaty, or incompatible with the treaty’s object and purpose.
Any Phrasing or Name
Includes reservations (excluding provisions) and interpretative declarations (clarifying understanding).
Modifying or Excluding Provisions
Exclusion: State rejects the provision’s content. Modification: State accepts the substance but with different terms.
Other states can accept, remain silent, or object to reservations:
Acceptance
Creates bilateral relations under the treaty between reserving and accepting states, with the reservation’s provisions applying.
Objections
Simple
Objecting state accepts the reserving state as a party, maintaining bilateral relations except in the reserved area.
Qualified
Objecting state rejects the reserving state as a party, precluding bilateral relations. Relations with other treaty parties remain unaffected.
Relationship Between Treaty and Custom
Treaties and customs are formal sources of international law with equal rank, but they interact (Article 38, 1969 Convention). Treaty rules can become customary law, binding all states except persistent objectors.
Professor Jimenez de Arechaga’s triple effect:
Declaratory Effect
Treaty codifies existing customary law.
Crystallizer Effect
Treaty solidifies a forming customary rule.
Generator Effect
Treaty initiates the formation of a new customary rule.