An organisation that wants its expertise in front of the European Court of Human Rights does not become a party to the case. It asks for leave to intervene as a third party, on a short written request, within a window that starts without anyone notifying it. This page sets out who may intervene, when the clock starts, what the request and the comments must contain, and what an intervener does and does not get at the end.
The twelve weeks run from a HUDOC publication that nobody sends you. We watch for communicated cases in your field, so the window is identified when it opens rather than after it closes — then draft the request for leave and the written comments to the President’s conditions.
At a glance
| Third-party intervention | Position under the Convention and the Rules of Court |
|---|---|
| Legal basis | Article 36 § 2 of the Convention, or Article 3, second sentence, of Protocol No. 16; Rule 44 of the Rules of Court |
| Who may ask | A Contracting State that is not a party, or “any person concerned who is not the applicant” |
| Test | Whether intervention would be in the interests of the proper administration of justice. It is not a right; it is at the Court’s discretion |
| Main deadline | Twelve weeks from publication on HUDOC that notice of the application has been given to the respondent State |
| The request | In writing, in English or French, normally not more than two pages; by post, or by fax and post. Email is not accepted |
| What leave normally covers | Written comments. Taking part in a hearing only in exceptional circumstances |
| Comments | Normally not more than ten pages, excluding annexes, within a time-limit fixed by the President |
| Costs | Third parties bear their own costs, cannot be awarded just satisfaction and are not entitled to legal aid |
What intervention is for — and what it is not
The purpose is to let the Court hear views from States and others who are not parties, and to be presented with information or arguments that are broader than, or different from, what the parties have put forward. An intervener’s role is to put legal or factual points before the Court as impartially and objectively as possible.
The Court’s practice direction then draws the boundary, and it is a firm one. Third parties are not entitled to express support directly for one side or the other, to make requests about the procedure, to seek a remedy from the Court, to take part in friendly-settlement negotiations between the parties, or to seek relinquishment or referral of a case to the Grand Chamber. An intervention is not advocacy for a party by another route.
What an intervener does get is this: all third-party submissions are placed in the file before the formation of the Court deliberating on the case, and may be referred to in the resulting decision or judgment.
Who can intervene
Article 36 § 2 rests on two separate limbs: any Contracting Party that is not a party to the proceedings, and “any person concerned who is not the applicant”. That second phrase is broader than it sounds, and the Court divides it into two groups — amici curiae and “interested third parties”. For any would-be intervener, whichever limb applies, there is no requirement of a direct legal interest in the outcome, and no requirement to be a national of, or based in, a Contracting State.
- Amici curiae. Non-governmental organisations, academics, private individuals, business enterprises, other international organisations, other Council of Europe bodies and independent national human-rights institutions. Their interest lies in providing submissions that may assist the Court — they may have an indirect interest in the case, a broader interest in its outcome, or no tangible interest at all.
- Interested third parties. Those whose legal rights may be affected, even indirectly, by a finding of a violation — for instance the applicant’s opponent in the domestic civil proceedings that gave rise to the application, or the other parent in a child-custody case. Their usual reason for intervening is that a violation may lead to the reopening of the domestic proceedings or to other individual execution measures affecting their position.
- States (the first limb). Contracting States other than the State of the applicant’s nationality normally have a legitimate interest, since the Court’s judgments elucidate and develop the Convention beyond the respondent State. Non-Contracting States are not covered by that limb but may seek leave under “any person concerned”, and must likewise have a legitimate reason.
One group is normally excluded. State authorities — legislatures, courts, local or regional authorities — are not usually considered entitled to intervene, because in international litigation the authorities of a State should in principle be represented by its central government. That applies to the authorities of the respondent State and of any other State alike.
Intervention under Article 36 § 2 should not be confused with the right of the State of the applicant’s nationality to intervene under Article 36 § 1. That is a right; this is a discretion.
The twelve-week window, and why it is easy to miss
Nobody writes to a prospective intervener. The main time-limit runs from a publication, and an organisation that is not watching for it will simply find the window closed.
- After notice of the application is given to the respondent State: twelve weeks, running from the day the information that notice has been given is published on HUDOC, the Court’s case-law database. The President of the Chamber may fix a shorter or longer period.
- To take part in a Chamber hearing: not later than four weeks after the information about the decision to hold an oral hearing is published on the Court’s website. This is possible only in exceptional cases.
- After relinquishment to the Grand Chamber, or after the panel accepts a referral request: twelve weeks from publication of that information on the Court’s website.
- In Protocol No. 16 advisory-opinion proceedings: normally eight weeks from publication of the panel’s decision to accept the request.
- Before the panel decides whether to accept a referral under Article 43: intervention is not possible at all, and earlier third-party comments are not put before that panel.
For observing the time-limit, what counts is the certified date of dispatch of the request, or, if there is none, the date it reaches the Registry. The Court’s own advice is not to wait for the end of the period but to seek leave as soon as practicable — sound advice, since the Court does not consult the parties before deciding, and a late request has nothing to argue about.
One point in favour of interveners: leave to submit written comments remains valid through the subsequent stages of the proceedings, so leave granted before a Chamber carries over to the Grand Chamber.
How to apply for leave: the two-page request
The request must be succinct — normally not more than two pages — and must identify the name and number of the case. Within that space it has to give the Court enough to assess whether intervention would serve the proper administration of justice:
- who the would-be third party is, with a postal and, if available, email address;
- any links between the would-be third party and any of the parties to the case;
- the reasons for wishing to intervene;
- any special knowledge of an issue arising in the case;
- the points on which submissions are proposed, and, as far as practicable, why those submissions will be useful to the Court and different from those of the parties or other third parties;
- whether the proposal is for written comments, participation in a hearing, or both.
The request must be in English or French. An initial request may be in an official language of a Contracting State, followed by a translation within a time-limit set by the President. It must be submitted in writing and sent by post, or by fax and post; filing by email is not accepted.
The ten-page limit and the President’s conditions
Leave comes with conditions set by the President. The substantive ones are that the comments carry the case name and number, bear a title identifying the third party, and do not exceed ten pages — annexes are outside the limit but must not be a continuation of the comments. The rest are formal: paper size, margins, type size, consecutive pagination, numbered paragraphs, indented long quotations and a reference for every document mentioned. Non-compliance is a ground for keeping the comments out of the case file, which is why we take that part on rather than send you a checklist.
The content conditions are where good interventions are won and lost:
- An amicus curiae should not touch upon the particular circumstances of the case, or on admissibility or the merits as such. It deals with the general issues the case raises, usually on the basis of its own expertise. This is the condition most often breached by organisations writing their first intervention.
- An intervening State should address solely the aspects relevant to its own interest in the case.
- An “interested third party” should address solely the factual and legal aspects relating to its specific interest.
Comments are filed in three copies by post, or in one copy by fax followed by three by post, or electronically under the relevant practice direction; email is not accepted. If the conditions are not met, the President may refuse to include the comments in the case file, or direct that fresh comments be submitted. Where two or more third parties have leave, the Court may direct them to file jointly. The parties are entitled to reply to the comments; third parties are not entitled to respond in turn.
Where a hearing is allowed — exceptionally — oral submissions are usually limited to ten minutes, and several interveners may be asked to designate one or two speakers between them.
Who pays: costs, legal aid and just satisfaction
Third parties cannot be awarded just satisfaction: Article 41 provides for it only for the injured party. They bear their own costs and expenses, and they are not entitled to legal aid from the Court, which is available to applicants. A third party may also be ordered to bear the costs of a witness or expert called at its request during an investigation by the Court.
At the end, every third party is informed of the Court’s judgment, decision or advisory opinion and is sent a copy — including interpretation judgments and judgments in infringement proceedings.
Representation is optional for interveners other than States, which act through their Agent. A third party that chooses to be represented is subject to the same prohibitions as a party on instructing a former judge of the Court, a sitting ad hoc judge, or a person on a current list of persons designated as eligible to serve as ad hoc judges.
How we support interveners
- Case monitoring. Watching HUDOC for communications in your field so the twelve-week window is identified when it opens, not after it closes.
- Viability and positioning. Whether your organisation falls within “any person concerned”, which group it belongs to, and what it can say that the parties will not.
- Drafting the request for leave within the two-page norm, covering each of the required points.
- Drafting and compliance of the comments. Keeping an amicus submission to the general issues, within the page and formatting conditions, and properly referenced.
- Filing. Through the channels the Court accepts, with dispatch evidence that fixes the material date.
- Coordination. Joint submissions with other organisations where the Court directs it or where it strengthens the submission.
Advisory opinions under Protocol No. 16
Protocol No. 16 proceedings begin with a request from a national court about a case pending before it, and the Court’s opinion is intended to guide that court. The parties to the domestic case are in a special position: they should normally be able to intervene and are systematically invited to do so, without needing to seek leave, even where they are State authorities. Other would-be interveners seek leave in the ordinary way, normally within eight weeks of publication of the panel’s decision to accept the request. Intervention before that panel is not possible.
Discuss a third-party intervention
In the message field, tell us the case (name and application number if you have them, otherwise the subject matter and respondent State), your organisation and its field of expertise, and whether notice of the application has already been published on HUDOC. A few lines are enough. Contacting us does not create a lawyer-client relationship, and nothing on this page is advice on an individual matter.
Related: admissibility conditions, the Rule 47 application form, and what happens after judgment.
Sources: Article 36 of the Convention, Rule 44 of the Rules of Court, and the Court’s Practice Direction on third-party intervention, issued on 13 March 2023 and amended on 1 October 2026.
Frequently Asked Questions
Does an NGO need a legal interest in the case to intervene?
No. Unlike the position in some national jurisdictions, a would-be third party is not required to have a direct legal interest in the outcome. It may have an indirect interest, a broader interest, or no tangible interest at all. What it must show is that its submissions would serve the interests of the proper administration of justice.
When exactly does the twelve weeks start?
From the day the information that notice of the application has been given to the respondent State is published on HUDOC — not from the date of the application, and not from any communication to your organisation. The President of the Chamber may set a shorter or longer period in a particular case.
Can a third party argue that the applicant should win?
No. Third parties are not entitled to express support directly for one or the other party. An amicus curiae is also expected to stay off the particular circumstances of the case and off admissibility and the merits as such, and to address the general issues instead. Comments that ignore this may be kept out of the case file.
Can a company intervene?
Business enterprises are expressly within the category of “any person concerned” that may act as amici curiae. Whether leave is granted turns on what the enterprise can contribute that the parties cannot, and its links with the parties must be disclosed in the request.
Can we take part in the hearing?
Only in exceptional circumstances, and the request must be made within four weeks of the publication of the information that a hearing will be held. If leave is given, oral submissions are usually limited to ten minutes.
Can you guarantee that leave will be granted?
No. Intervention is at the Court’s discretion and it does not consult the parties before deciding. What can be done is to file within the window, keep the request to the points the Court asks for, and say something the parties and the other interveners will not — which is what the decision actually turns on.
Will our costs be covered?
No. Third parties bear their own costs and expenses, cannot be awarded just satisfaction, and are not entitled to legal aid from the Court. The exception is narrow: parties to the domestic case invited to intervene in Protocol No. 16 proceedings may seek legal aid if they lack sufficient means.