W1 - System and sources of IL
Jus Naturale Universal, inherent moral principles and rights discoverable through human reason. It was distinguished from
(Natural Law) jus gentium (law of nations) by thinkers like Grotius.
Jus Gentium (Law of Developed out of the late medieval tradition; it is seen as emerging from human interaction/society/sociability,
Nations) in contrast to jus naturale.
Jus ad Bellum The rules that set the conditions under which states may legally resort to armed force (the law on going to
war).
Jus in Bello The rules that regulate the conduct of parties engaged in an armed conflict (International Humanitarian Law),
primarily to minimize suffering.
Soft law = Name given to the body of standards, commitments, declara ons, policy guidelines, codes of conduct and other instruments which do not impose legally binding obliga
on on States or any other legal actor for that matter
- is an another possible source of law -Potential to contribute to the development of hard law
Pacta sunt servanda = treaties must be performed in good faith
Opinio juris = an opinion of law or necessity = refers to the subjective belief held by states that a particular practice is not merely a matter of custom, convenience, or political
expediency, but is instead carried out because it is legally obligatory.psychological element that transforms state practice into binding customary IL.
- presence of opinio juris transforms a consistent pattern of behavior into a legally binding rule
Lotus (PCIJ) 1927 - consent = basis of obligation, sovereignty presumed
"International law governs relations between independent States. The rules of law binding upon States therefore emanate from their own free will as
expressed in conventions or by usages generally accepted as expressing principles of law .... Restrictions upon the independence of States cannot
therefore be presumed." (PCIJ,
North sea continental = defined CIL elements, stressed opinio juris
shelf case
Nicaragua (ICJ) custom can bind even non treaty parties, affirmed principle of non intervention
- In international law there are no other than such rules as may be accepted by thestate concerned, by treaty or otherwise whereby the
level of armaments of a sovereign state can be limited, and this principle is valid for all States without exception
,Western sahara -1975 (context : process of decolonisation in the 60s)
rejected terra nullius, recognised indigenous sovereignty
Nuclear tests - 1974 unilateral declarations can create legal obligation s
SOURCES of IL
- coherent but decentralised system
- Rule making depends on consent, yet shaped by hierarchy (jus cogens, HR)
- UN charter : constitutional document of modern IL
Art 38 ICJ statute
- = traditional starting point of international legal sources
- Lays out that ICJ’s function ‘is to decide in accordance with international law’
- But modern practice blurs boundaries with soft law & institutional acts
- 38b - customary IL = recurring interaction among individuals and groups that is accompanied by the acknowledgment that such a mode of interaction produces
certain expectations of conduct that ought to be satisfied
- 2 Elements of Custom
(1) Material element = relating to the actual practice of States in their relations →Usus = usage
(2) Subjective element =Opinion juris = belief of States that such behaviour is ‘law’ necessitates = an opinion as to law or necessity
→difficulty to identify customs bc custom is relative
→exceptions where custom is not universal : persistent and subsequent objection / local,regional and bilateral custom / enduring relevance of custom
- art 38a : treaties and conventions in force -treaties = Formal instrument through which States can agree that certain obligations will be binding between
them
= are, by far, the predominant source of rights and obligations in today’s international legal order
- Pact sunt servanda = agreement shall be kept - Art. 26 VCLT
- art 38c : general principles
= recognition of ‘general principles’ arose from a concern by the drafters of the PCIJ Statute that the Court might, in future, find that there were no treaty or
customary rules which could resolve a dispute alone.
- general principles recognized to civilised nations also constitute a source of IL
, HIERARCHY of norms in IL :
- jus cogens (= art 53 VCLT) are at the top of the hierarchy when it comes to hierarchy of norms
- Non-derogable in all circumstances
- Nullity of a treaty in conflict (Art. 64 VCLT)
- Norms applicable to all States
- Accepted and recognized as peremptory by int. community of States as a whole
- Starting point (not final word)
- Eg :
- Acts of aggression -use of force (only exception - art 51 UN charter , self defence)
- Genocide
- War Crimes & Crimes against Humanity
- Prohibition against Torture
- Prohibition against Slavery and Slave Trade
- Systematic Racial Oppression (in particular apartheid)
- Obligation erga omnes = Category of rights owed to all which have a special status within IL
- great overlap between them : for eg : the prohibi ons against genocide and torture are simultaneously norms of jus cogens and obliga ons erga omnes
!!!!! However, one should remain wary of the fact that arguments grounded in jus cogens have rarely been invoked by States, and still more rarely prevailed before international courts and
tribunals.
HISTORY of IL
TWAIL = Third World Approaches to International Law
Classical period : 1600-1815 : IL seen as a dual system:
- Natural law = universal, eternal, based on reason.
- Law of nations (jus gentium) = created by states (custom/treaty), variable, binding only by consent.
Statements of the origins of IL :
J Crawford: Brownlie's Principles of Public International Law (9th Edition) (2019) pp. 3-4 [first lines]
- 'The law of nations, now known as (public) IL, developed out of the tradition of the late medieval jus gentium. Through an influential series of writers - Victora, Gentili,
Grotius, Pufendorf, Wolff, Vattel, and others - it came to be seen as a specialised body of legal thinking about the relations between rulers.'
J Klabbers
- 'By general acclamation, the history of modern IL (international law as we know it) is usually said to have started in the 17th c'
G Hernandez (2025)
- '1648 Peace of Westphalia, often taken as the conceptual starting point for modern international law in the European State system…'
, Treaty of Vienna 1815 = beginning of the idea of sovereignty of states. Reinstated the hereditary legitimacy of the sovereignty of states
- Restored ‘legitimate’ order in Europe through
1. Balance of power - equality
2. Recognised principles (no more revolutions pls, )
- This restored order through a balance of power and recognized principles (respect for hereditary legitimacy). Crucially, it demonstrated
sovereign equality operating simultaneously with legalized hierarchy. This is summarized by the critical takeaway: "domination through
equality"
Berlin conference 1885 (context : new discoveries of water courses in uganda )
- - Aims :
1. Freedom of navigation of congo rivers
2. Agreeing on rules concerning acquisition
- This “Transformed africa into a conceptual terra nullis” (Anghie)
Mandate system - art 22 - The mandate power have authority over other parts of the world
LoN - ‘Tutelage of such people should be entrusted to advanced nations [...]’
- =justification of imperialism
- Visible separation of the world in between those capable of sovereignty and those deemed backward in need of tutelage
KEY FIGURE Contribution
Francisco de Vitoria - a primitive thinker on the origin of IL, a forerunner to Grotius.
(16th C theologian ) - his work was directly aimed at providing a legal framework for Spanish colonialism.
- Justifies colonialism :
- He provided a legal answer to a legal question that was blocking colonial expansion. he constructed a legal framework that resolved the
theoretical dilemma in a way that systematically favors Spanish interests -
- he creates jus gentium which is a new source of law : a secular and universal law
Jus gentium= natural law= law of nations
=discusses the rules that should govern interactions between peoples
- secular: Vitoria dismantled the old justifications (Pope's authority, Emperor's lordship) for
conquest = q of : what law does apply between two such diff people- problem of jurisdicition w
no clear authority
- universal: applies to all those w reason, bc it is based on reason from human reason and is
natural. Based on "natural reason" that supposedly applied to everyone, everywhere.
- jus gentium is the precursor of IL (au 16e IL doesn’t exist- but this is the basis that will become it)
-
Jus Naturale Universal, inherent moral principles and rights discoverable through human reason. It was distinguished from
(Natural Law) jus gentium (law of nations) by thinkers like Grotius.
Jus Gentium (Law of Developed out of the late medieval tradition; it is seen as emerging from human interaction/society/sociability,
Nations) in contrast to jus naturale.
Jus ad Bellum The rules that set the conditions under which states may legally resort to armed force (the law on going to
war).
Jus in Bello The rules that regulate the conduct of parties engaged in an armed conflict (International Humanitarian Law),
primarily to minimize suffering.
Soft law = Name given to the body of standards, commitments, declara ons, policy guidelines, codes of conduct and other instruments which do not impose legally binding obliga
on on States or any other legal actor for that matter
- is an another possible source of law -Potential to contribute to the development of hard law
Pacta sunt servanda = treaties must be performed in good faith
Opinio juris = an opinion of law or necessity = refers to the subjective belief held by states that a particular practice is not merely a matter of custom, convenience, or political
expediency, but is instead carried out because it is legally obligatory.psychological element that transforms state practice into binding customary IL.
- presence of opinio juris transforms a consistent pattern of behavior into a legally binding rule
Lotus (PCIJ) 1927 - consent = basis of obligation, sovereignty presumed
"International law governs relations between independent States. The rules of law binding upon States therefore emanate from their own free will as
expressed in conventions or by usages generally accepted as expressing principles of law .... Restrictions upon the independence of States cannot
therefore be presumed." (PCIJ,
North sea continental = defined CIL elements, stressed opinio juris
shelf case
Nicaragua (ICJ) custom can bind even non treaty parties, affirmed principle of non intervention
- In international law there are no other than such rules as may be accepted by thestate concerned, by treaty or otherwise whereby the
level of armaments of a sovereign state can be limited, and this principle is valid for all States without exception
,Western sahara -1975 (context : process of decolonisation in the 60s)
rejected terra nullius, recognised indigenous sovereignty
Nuclear tests - 1974 unilateral declarations can create legal obligation s
SOURCES of IL
- coherent but decentralised system
- Rule making depends on consent, yet shaped by hierarchy (jus cogens, HR)
- UN charter : constitutional document of modern IL
Art 38 ICJ statute
- = traditional starting point of international legal sources
- Lays out that ICJ’s function ‘is to decide in accordance with international law’
- But modern practice blurs boundaries with soft law & institutional acts
- 38b - customary IL = recurring interaction among individuals and groups that is accompanied by the acknowledgment that such a mode of interaction produces
certain expectations of conduct that ought to be satisfied
- 2 Elements of Custom
(1) Material element = relating to the actual practice of States in their relations →Usus = usage
(2) Subjective element =Opinion juris = belief of States that such behaviour is ‘law’ necessitates = an opinion as to law or necessity
→difficulty to identify customs bc custom is relative
→exceptions where custom is not universal : persistent and subsequent objection / local,regional and bilateral custom / enduring relevance of custom
- art 38a : treaties and conventions in force -treaties = Formal instrument through which States can agree that certain obligations will be binding between
them
= are, by far, the predominant source of rights and obligations in today’s international legal order
- Pact sunt servanda = agreement shall be kept - Art. 26 VCLT
- art 38c : general principles
= recognition of ‘general principles’ arose from a concern by the drafters of the PCIJ Statute that the Court might, in future, find that there were no treaty or
customary rules which could resolve a dispute alone.
- general principles recognized to civilised nations also constitute a source of IL
, HIERARCHY of norms in IL :
- jus cogens (= art 53 VCLT) are at the top of the hierarchy when it comes to hierarchy of norms
- Non-derogable in all circumstances
- Nullity of a treaty in conflict (Art. 64 VCLT)
- Norms applicable to all States
- Accepted and recognized as peremptory by int. community of States as a whole
- Starting point (not final word)
- Eg :
- Acts of aggression -use of force (only exception - art 51 UN charter , self defence)
- Genocide
- War Crimes & Crimes against Humanity
- Prohibition against Torture
- Prohibition against Slavery and Slave Trade
- Systematic Racial Oppression (in particular apartheid)
- Obligation erga omnes = Category of rights owed to all which have a special status within IL
- great overlap between them : for eg : the prohibi ons against genocide and torture are simultaneously norms of jus cogens and obliga ons erga omnes
!!!!! However, one should remain wary of the fact that arguments grounded in jus cogens have rarely been invoked by States, and still more rarely prevailed before international courts and
tribunals.
HISTORY of IL
TWAIL = Third World Approaches to International Law
Classical period : 1600-1815 : IL seen as a dual system:
- Natural law = universal, eternal, based on reason.
- Law of nations (jus gentium) = created by states (custom/treaty), variable, binding only by consent.
Statements of the origins of IL :
J Crawford: Brownlie's Principles of Public International Law (9th Edition) (2019) pp. 3-4 [first lines]
- 'The law of nations, now known as (public) IL, developed out of the tradition of the late medieval jus gentium. Through an influential series of writers - Victora, Gentili,
Grotius, Pufendorf, Wolff, Vattel, and others - it came to be seen as a specialised body of legal thinking about the relations between rulers.'
J Klabbers
- 'By general acclamation, the history of modern IL (international law as we know it) is usually said to have started in the 17th c'
G Hernandez (2025)
- '1648 Peace of Westphalia, often taken as the conceptual starting point for modern international law in the European State system…'
, Treaty of Vienna 1815 = beginning of the idea of sovereignty of states. Reinstated the hereditary legitimacy of the sovereignty of states
- Restored ‘legitimate’ order in Europe through
1. Balance of power - equality
2. Recognised principles (no more revolutions pls, )
- This restored order through a balance of power and recognized principles (respect for hereditary legitimacy). Crucially, it demonstrated
sovereign equality operating simultaneously with legalized hierarchy. This is summarized by the critical takeaway: "domination through
equality"
Berlin conference 1885 (context : new discoveries of water courses in uganda )
- - Aims :
1. Freedom of navigation of congo rivers
2. Agreeing on rules concerning acquisition
- This “Transformed africa into a conceptual terra nullis” (Anghie)
Mandate system - art 22 - The mandate power have authority over other parts of the world
LoN - ‘Tutelage of such people should be entrusted to advanced nations [...]’
- =justification of imperialism
- Visible separation of the world in between those capable of sovereignty and those deemed backward in need of tutelage
KEY FIGURE Contribution
Francisco de Vitoria - a primitive thinker on the origin of IL, a forerunner to Grotius.
(16th C theologian ) - his work was directly aimed at providing a legal framework for Spanish colonialism.
- Justifies colonialism :
- He provided a legal answer to a legal question that was blocking colonial expansion. he constructed a legal framework that resolved the
theoretical dilemma in a way that systematically favors Spanish interests -
- he creates jus gentium which is a new source of law : a secular and universal law
Jus gentium= natural law= law of nations
=discusses the rules that should govern interactions between peoples
- secular: Vitoria dismantled the old justifications (Pope's authority, Emperor's lordship) for
conquest = q of : what law does apply between two such diff people- problem of jurisdicition w
no clear authority
- universal: applies to all those w reason, bc it is based on reason from human reason and is
natural. Based on "natural reason" that supposedly applied to everyone, everywhere.
- jus gentium is the precursor of IL (au 16e IL doesn’t exist- but this is the basis that will become it)
-
