The European Case Law Identifier (ECLI) is an identifier for court decisions in Europe. The identifier consists of five elements separated by colons: ECLI:[country code]:[court identifier]:[year of decision]:[specific identifier].^[1] The standard is laid down in the Council Conclusions inviting the introduction of the European Case Law Identifier (ECLI) and a minimum set of uniform metadata for case law of the European Union.^[2] The ECLI framework also contains a set of uniform metadata to improve search facilities for case law. Court decisions that have an ECLI assigned can be indexed by the ECLI Search Engine of the European e-Justice portal.

The concept of ECLI was first^[3] launched at the Legal Access Conference (Paris, December 2008)^[4] and at Jurix Conference on Artificial Intelligence and Law in Florence (December 2008).^[5] Around the same time, the study by a task group of the EU Council Working Group on e-Law showed that accessibility of judicial decisions, both at the national and European level, was seriously hampered by the lack of standardised identifiers and metadata:

The task group suggested to establish a voluntary common identification system based on the European Case-Law Identifier (ECLI). ECLI as an identifier would be linked to an index with references. This would enable any citizen or legal practitioner to find any decision to which ECLI has been attributed from any public or private register or database in the EU. In addition a Dublin-core implementation for case-law should be established to facilitate searching case-law in different search engines.^[6]

Based on the report of this task group, the Council of Ministers agreed on the principles of ECLI and common metadata, and asked the EU Council Working Party on Legal Data Processing (e-Law) to elaborate the initial work.^[6] This continued work resulted in the Council Conclusion inviting the introduction of the European Case Law Identifier (ECLI) and a minimum set of uniform metadata for case law of the European Union,^[2] decided upon by the Council of Ministers on 22 December 2010. It was published in the Official Journal of 29 April 2011 (2011/C 127/01).

ECLI does not primarily identify a paper or electronic document containing a judgment, but instead identifies the court decision at a more abstract level. In the terminology of the Functional Requirements for Bibliographic Records on which it is based, ECLI is a work-level identifier. It is constructed with the intention to be meaningful, open, technological neutral, recognisable for both humans and computers, error-proof and interoperable with other identifiers.^[7] The formatting rules for ECLI are prescribed in detail in the Annex to the Council Conclusions. Summarized, an ECLI always consists of five parts, separated by a colon:

• 'ECLI' as a self-identifier;
• The country code, prescribed by the interinstitutional style guide of the EU.^[8] The standard uses mostly ISO 3166-1 alpha-2 codes with the exception of the United Kingdom (UK) and Greece (EL). A special code for non-states can be assigned by the European Commission;
• The court code, to be assigned by the national ECLI co-ordinator; it has a maximum length of seven positions;
• The year the judgment is rendered, written in four digits;
• A unique code to make an ECLI unique. The maximum length of this code is 25 characters. Only letters, digits and dots are to be used, other punctuation marks or whitespace are not allowed. Pre-existing national identifiers can be used for this fifth part, of which the date of judgment can be a part too. Also a serial number which is generated especially for ECLI is possible. It is up to the national ECLI co-ordinator to decide on the construction of this last part.

Only the Latin alphabet is to be used, and that ECLI is case-insensitive, although it is written preferably in capitals. An example of a case law identifier of the Dutch Supreme Court is ECLI:NL:HR:1841:1,^[9] which indicates a Dutch decision (NL) of 1841 of the Supreme Court (HR) with serial number 1.

According to paragraph 4 of the Annex to the Council Conclusions an ECLI website has to be set up, containing

• general information on ECLI;
• a list of participating countries, with, for each country:
  • the court codes used;
  • information on the formatting of the fifth part of the ECLI code;
  • information on the national ECLI co-ordinator.

The ECLI website was set up within the frame work of the e-justice portal of the European Union.

According to paragraph 5 of the Annex to the Council Conclusions an ECLI Search Engine has to be set up, enabling search by ECLI and metadata. This ECLI search engine launched on 4 May 2016. It provides access to national and European case law, stored in whatever database. Searches are possible on the basis of the ECLI, its metadata as well as full-text.

As prescribed by the Council Conclusions a resolver is available at https://e-justice.europa.eu/ecli/; with an ECLI typed after it, this link with show all available information on this ECLI, from whatever indexed website. As an example: https://e-justice.europa.eu/ecli/ECLI:CZ:NS:2015:32.CDO.2051.2013.1 shows from ECLI:CZ:NS:2015:32.CDO.2051.2013.1, a decision from the Czech Supreme Court, the information from the website of that court as well as from the Jurifast database of the Association of Councils of State and Supreme Administrative Jurisdictions of the EU. The latter document also has English and French metadata.

Documents are indexed by the ECLI search engine in cooperation between the European Commission and data providers, using the sitemaps protocol and robots.txt.^[10]

The Council of Ministers is responsible for any future changes in the standard, while the European Commission is responsible for the ECLI-website and the maintenance of the ECLI Search Engine.

According to the Council Conclusions, Member States are free to decide on their own implementation route. A big-bang scenario is possible, but also a step-by-step approach is allowed. International organizations may also participate and can request a "country code" from the European Commission.

The table below lists all EU Member States and their current state of ECLI implementation. Also relevant European organisations that have implemented ECLI are included.

Metadata are to be attached to documents containing a judicial decision. They can relate to the ECLI itself (on the bibliographic work level, e.g.: date of the decision), but also to a specific editorial version (the 'expression level', e.g. a summary). In the Council Conclusions nine mandatory and eight optional metadata are listed. All these are based on the Dublin Core metadata standard. The mandatory means that without these metadata, a document can not be indexed by the ECLI Search Engine.

• European Legislation Identifier (ELI)
• Lex (URN)