Introduction to treaties[edit]

A treaty is defined as a "written agreement by which two or more states or international organisations create or intend to create a relation between themselves operating within the sphere of international law". [1]

Treaties can be loosely compared to contracts, in that the parties willingly assume binding obligations among themselves, and any party that breaches its obligations can be held liable under international law.

Types of treaties[edit]

It is important to know the type of treaty as the research tools or databases may only look at one type of treaty or may deal with the two types differently.

Bilateral treaties are between two states or entities.

Multilateral treaties are between multiple states, countries, or entities often observing rights and obligations between each party and every other party.

Stages of a treaty[edit]

Signing – Treaties often begin with discussions, where there will be negotiations resulting in an agreed text. The parties to the treaty sign, but it is not yet legally binding. In the UK, treaties that require ratification are laid before Parliament under the Ponsonby rule 21 days before ratification. The date in which a treaty is important as some resources arrange treaties chronologically by date of signature. Occasionally, the treaty will state that it will come into force on signature.

Ratification – This stage follows signing and signifies the consent of a state or entity to be bound by the treaty. It consists of the deposit of an instrument of ratification with the other state (if bilateral), or the depositary (if multilateral). States which accede to a treaty is where a state becomes party to a treaty that is already in force; accession has the same effect as ratification.

In force – This is the date the treaty comes into force and will be stated within the treaty itself. However, the date is often indeterminate as it will usually depends on subsequent events e.g. the UN Convention on the Law of the Sea 1982, states that it will come into force after the 60th country has ratified it.

Adding and amending a treaty[edit]

Reservations are made when a state wishes to limit its treaty obligations, in turn these reservations become unilateral statements which exclude or modify a state's legal obligation (and its effects). These reservations must be included at the time of signing or at the ratification stage. Other states party a treaty where one state proposes reservations have the option to accept, object, or oppose. If a state chooses to accept, then the reserving state(s) and accepting state(s) are relieved of their legal obligation to one another. If a state chooses to object or oppose, then it essentially refuses to acknowledge the reserving state is a party to the treaty.

A treaty can be amended in three different ways:

  • a formal amendment requires states or parties to a treaty to enter the ratification stage again
  • an informal amendment requires the treaty executive council; this is often for changes that are procedural
  • rectifying minor corrections, such as changes in international law or obvious errors within the text (i.e. reflecting the intentions of the parties)

A protocol is a treaty which amends or supplements an earlier principal treaty or international agreement. It can amend the previous treaty, or add additional provisions. Parties to the earlier agreement are not required to adopt the protocol, which is further acknowledge by calling it an "optional protocol", especially where many parties to the first agreement do not support the protocol.

Ending treaty obligations[edit]

Withdrawal - treaties are not necessarily permanently binding upon the signatory parties, allowing for withdrawal. However, many treaties expressly forbid withdrawal, so this ultimately this depends on the wording of the treaty. If allowed within the wording, then states must follow a procedure to notify their intention of withdrawal. If successful, then its obligations under a multilateral treaty are considered terminated but the treaty remains in force amongst other parties or states, and if a bilateral treaty, then withdrawal terminates the treaty in its entirety.

Alternatively, a state may withdraw from a treaty and cease to abide by its terms, especially in case where withdrawal is not allowed. The question of lawfulness usually will depend on how other states signatory to the treaty will react - either imposing sanctions or declaring war.

If a state has breached its treaty obligations, then other parties may consider this as grounds for suspending and/or terminating their obligations under the treaty. Similar to withdrawal, a treaty breach does does not automatically suspend or terminate a treaty - it depends on how other parties view and respond to the breach.

However, some treaties include provisions for self-termination, which mean the treaty is automatically terminated if certain conditions are not met, or if the treaty is temporarily binding and is set to expire at a given date.


A consequence of using the word treaty suggests the parties are both sovereign states and the agreement is enforceable under international law. An example where this isn't the case is within the United States, where agreements between states are called compacts and agreements between states and the federal government (or between agencies of the government) are memoranda of understanding. Another example is where one party wishes to create an obligation under international law, but the other party does not.

A Memorandum of Understanding (MOU), different to the US term, is an informal record of a non-legally binding arrangement between states on matters that are considered unsuitable for inclusion in treaties. The terminology used in MOUs is different from the terminology used in treaties. For example, the UK does not publish MOUs and does not register them at the UN. In addition to this, they may not be deposited at the National Archive until many years later.

An explanatory memorandum may accompany a treaty and provides information about the treaty.

Format and citation[edit]

  • Preamble - opening sentence, often long, noting the "High Contracting Parties" and their shared objectives in executing the treaty, as well as summarizing any underlying events
  • Main elements – title, date of signature, and (for multilateral treaties) place of signature
  • Title – every treaty has a formal title, but an abbreviated form may be commonly used e.g. European Convention on Human Rights (original formal title: Convention for the Protection of Human Rights and Fundamental Freedoms)
  • Date of signature – usually essential to know for tracing purposes
  • Place of signature – not always essential, but often used in popular titles, e.g. the Warsaw Convention, the Treaty of Rome
  • Articles - the component sections of a treaty, these may be divided further into paragraphs and sub-paragraphs


Hardcopy sources[edit]

Glossary of terms

  • Modern Treaty Law and Practice by Anthony Aust (Cambridge University Press, 2013)
This book offers a glossary of terms used in treaties, held by the all Inns of Court.


  • Multilateral Treaties: Index and Current Status by Bowman and Harris (1984, supplement 1993) - for multilateral treaties whether UK is a party or not. Command Paper numbers and other citations are given. Inner Temple, Lincolns Inn and Gray’s Inn Libraries have this work.
  • Multilateral Treaty Calendar by Wiktor, 1648 -1995 – Inner Temple and Lincoln’s Inn Libraries have this book.
  • UN Treaty Series – all treaties made by members of the UN have to be registered with the UN Secretariat and published by it. Middle Temple Library has the UN Treaty Series in hard copy. There are chronological and alphabetical indexes.
  • League of Nations Treaty Series 1920-1946 – predecessor to the UN Treaty Series. Middle Temple Library has this.
  • International Legal Materials – this journal contains the texts of selected treaties. Inner Temple and Gray’s Inn Libraries have this series, 1962 onwards.
  • Index to British Treaties by Parry (1970) – gives information on the date of signing, entry into force, duration and parties.
  • British and Foreign State Papers - held by Inner Temple Library (1812-1968), Middle Temple (1812-1968), and Lincoln's Inn (1812-1832/33).
  • Hertslet’s Commercial Treaties (HCT) – covers 1827-1925. Inner Temple, Lincoln’s Inn and Middle Temple Libraries hold this series.

Command Papers

The following Inn Libraries hold Command Papers:

  • Inner Temple (1940/41 onwards)[2]
  • Lincolns Inn (1833 onwards)
  • Middle Temple (1861 onwards).

Online sources[edit]

  • United Nations Treaty Series Online Collection – contains a collection of treaties and international agreements registered or filed and recorded with and published by the Secretariat since 1946. It also includes a collection of treaties and subsequent treaty actions registered with and published by the Secretariat of the League of Nations between 1920 -1944.
  • Flare Index to Treaties – this site has information on over 2,000 of the most significant multilateral treaties. Each entry includes information about where the full text of each treaty can be found in print with live links to electronic versions on the internet, where available. The index covers treaties concluded between 1353 and the present. Searching can be done using subject keywords, words from the official or popular title, the reference number allocated to a treaty by either the Council of Europe or the International Labour Organization, the date on which the treaty was concluded (either the precise date or just the year), or the place where the treaty was concluded.
  • Eagle-i - an internet portal maintained and updated by IALS library staff. It allows you to search for quality web resources on treaties.
  • Council of Europe Treaty Office – has full text and summaries of the complete European Treaty Series (ETS) 1949-2003, and its continuation the Council of Europe Treaty Series (CETS) 2004 onwards.
  • WIPO Lex - provides a search facility for intellectual laws and treaties for a wide range of jurisdictions.
  • Treaties Office Database of the European External Action Service – this gives full status information of all the bilateral and multilateral treaties or agreements concluded by the European Community, the European Atomic Energy Community (EAEC) and the former European Coal and Steel Community (ECSC), and those concluded under the Treaty on European Union.
  • Websites of international organisations – some organisations act as depositaries or secretariats for certain multilateral treaties e.g. Hague Conference on International Law, WIPO etc.
  • UK Treaties – this section of the GOV.UK website provides information on the work of the Foreign & Commonwealth Office (FCO) Treaty section. There is a UK Treaties Online (UKTO) database containing records and full texts of treaties published since 1834. Most texts are held within the database itself: others may be found by following the links provided.
  • Official Documents – includes Command Papers in full text from 17 May 2005 to January 2014. Earlier Command Papers from 1994 to April 2005 can be found via the About Official Documents link. New Command Papers can be found on the GOV.UK: Publications site.

Foreign and Commonwealth Office[edit]

The FCO Treaty Enquiry Service (which is free of charge) is open from 0900 to 1700 Monday to Friday.

This service can give advice on whether a treaty has entered into force, details of the signatories and contracting parties, together with dates of signature, ratification, approval, acceptance, accession, succession and withdrawals or denunciations. Reservations, declarations or objections can usually be identified, and where applicable, the depositary.

Email:; Telephone: 020 7008 1109


  1. Lord McNair., (1961), The Law of Treaties, Oxford University Press, ISBN 9780198251521.
  2. in non-retrievable storage until 2021