The Council of Europe Treaty Series groups together all the conventions concluded within the Organisation since 1949. Whatever they are called ("agreement", "convention", "arrangement", "charter", "code", etc.), all these texts are international treaties in the sense of the Convention of Vienna of 1969 on the law of treaties.
The conventions of the Council of Europe are prepared and negotiated within the institutional framework of the Council of Europe. Negotiations culminate in a decision of the Committee of Ministers to adopt the final text of the proposed treaty. It is then agreed to open the treaty for signature by member States of the Council and, if necessary, by the other States or organisations who have taken part in its elaboration.
The great majority of the conventions of the Council of Europe make provision for non-member States of the Organisation to become Parties thereto, upon invitation by the Committee of the Ministers of the Council of Europe and by means of the procedure of accession.
The Secretary General is the depositary of the conventions of the Council of Europe. He is the custodian of these conventions and presides over their signature and the deposit of the instruments of ratification, acceptance, approval or accession.
The tasks related to the exercise of depositary functions are carried out by the Treaty Office, which is responsible for the day-to-day administration of the treaties of the Council of Europe. The Treaty Office publishes and is the custodian of the original texts of all the treaties and organises each ceremony of signature or ratification. It receives and registers the ratifications, as well as any declarations and reservations that accompany them, and any withdrawal or modification thereof. It ensures that the documents it receives are in due and proper form and is responsible for the notifications prescribed in the final clauses of the conventions to the member States of the Council of Europe and other States or organisations which are parties to the treaties. It arranges also for their registration with the Secretariat of the United Nations.
In addition to its functions as Depositary of Council of Europe Treaties, the Treaty Office also provides legal advice regarding such treaties as well as issues of public international law. In particular, the Treaty Office examines all draft treaties before they can be submitted to the Committee of Ministers, in conformity with Rule No. 1316 of 25 January 2011 defining the tasks and responsibilities of the Public International Law Division and Treaty Office within the Directorate of Legal Advice and Public International Law.