SECOND SECTION

CASE OF BOZYOKUŞ AND OTHERS v. TÜRKİYE

(Applications nos. 39586/20 and 131 others –

see appended list)

JUDGMENT
 

STRASBOURG

16 December 2025

This judgment is final but it may be subject to editorial revision.

In the case of Bozyokuş and Others v. Türkiye,

The European Court of Human Rights (Second Section), sitting as a Committee composed of:

 Jovan Ilievski, President,
 Péter Paczolay,
 Juha Lavapuro, judges,
and Dorothee von Arnim, Deputy Section Registrar,

Having regard to:

the applications against the Republic of Türkiye lodged with the Court under Article 34 of the Convention for the Protection of Human Rights and Fundamental Freedoms (“the Convention”) by the applicants listed in the appended table (“the applicants”), on the various dates indicated therein;

the decision to give notice of the complaints under Article 6 § 1 (the right to a fair trial) and Article 7 of the Convention (no punishment without law) to the Turkish Government (“the Government”) represented by their Agent, Mr Abdullah Aydın, Head of the Department of Human Rights of the Ministry of Justice of the Republic of Türkiye;

the parties’ observations;

the decision to reject the Government’s objection to the examination of the applications by a Committee;

Having deliberated in private on 25 November 2025,

Delivers the following judgment, which was adopted on that date:

SUBJECT MATTER OF THE CASE

1.  The case concerns the applicants’ convictions for membership of an armed terrorist organisation described by the Turkish authorities as the “Fetullahist Terror Organisation/Parallel State Structure” (Fetullahçı Terör Örgütü / Paralel Devlet Yapılanması, hereinafter referred to as “the FETÖ/PDY”), considered by the authorities to be behind the coup attempt that took place in Türkiye on 15 July 2016. The broader domestic background and context to the present applications was set out by the Court in Yüksel Yalçınkaya v. Türkiye ([GC], no. 15669/20, §§ 10-22 and 108-40, 26 September 2023).

2.  The applicants’ convictions were based decisively on their use of an encrypted messaging application by the name of “ByLock”. The domestic authorities and courts considered that the ByLock application was designed for the exclusive use of the members of the FETÖ/PDY and that the establishment of the use of that application was sufficient on its own for conviction under Article 314 § 2 of the Criminal Code for membership of an armed terrorist organisation (ibid., §§ 155-65 and 257).

3.  Other evidence against the applicants, if any, involved mainly an admission of using ByLock, decrypted message content confirming use of that application or witness statements attesting to such use; membership of a trade union, association and/or foundation considered to be affiliated with the FETÖ/PDY; account activities at Bank Asya, which was considered by the authorities to be a part of the financial structure of the FETÖ/PDY; possession of pro-FETÖ/PDY publications or other audio-visual material; participation in trips considered to have been organised by the FETÖ/PDY and records of exit from and entry to Türkiye; donations to FETÖ/PDY-affiliated foundations; participation in various demonstrations considered to be in support of the FETÖ/PDY or in other organisational activities; social media posts in favour of the organisation; residence in FETÖ/PDY student houses or dormitories; use of other messaging applications, such as Kakao Talk or Eagle, to communicate with other members of the organisation; HTS (Historical Traffic Search) records indicating communications with others prosecuted of the same offence or other digital evidence suggesting membership of the organisation; employment by and/or membership of FETÖ/PDY‑affiliated institutions, organisations or companies; witness statements as regards such employment and/or membership, or as regards other connections to the FETÖ/PDY. In the case of some of the applicants, the convictions were imposed without waiting for the submission to the case files of the detailed ByLock findings and evaluation reports – which potentially included decrypted content of communications over ByLock – on the ground that the establishment of the use of that application sufficed for conviction, irrespective of the nature and content of the communications.

4.  The individual applications lodged by the applicants with the Constitutional Court against their convictions were summarily dismissed by that court as being inadmissible, on the basis of its case-law endorsing the Court of Cassation’s landmark judgments on the matter (see Yüksel Yalçınkaya, cited above, §§ 169-88).

THE COURT’S ASSESSMENT

1. JOINDER OF THE APPLICATIONS

5.  Having regard to the similar subject matter of the applications, the Court finds it appropriate to examine them jointly in a single judgment.

2. ALLEGED VIOLATION OF ARTICLES 7 and 6 § 1 OF THE CONVENTION
   1. Alleged violation of Article 7 of the Convention

6.  The applicants complained that their convictions under Article 314 § 2 of the Criminal Code for membership of the FETÖ/PDY had violated the principle of no punishment without law under Article 7 of the Convention, primarily for the reasons set out in Demirhan and Others v. Türkiye (nos. 1595/20 and 238 others, § 29, 22 July 2025).

7.  The Government reiterated their observations as outlined in Demirhan and Others (ibid., §§ 31-34). They submitted that, while notice of the present applications had been given to them as raising issues similar to those addressed by the Court in Yüksel Yalçınkaya (cited above), the Court’s considerations in that judgment had related to the specific facts of that case. They argued that the Court should therefore refrain from extrapolating the findings made therein to the present applications and invited it to assess the criminal proceedings conducted against each applicant on the basis of their own particular circumstances. They claimed, in particular, that the convictions in the present applications had not been based solely on the applicants’ use of the ByLock application but had involved a wide variety of other evidence, not all of which had been subject to assessment in Yüksel Yalçınkaya (cited above; see the evidence listed in paragraph 3 above). The domestic courts, which had enjoyed direct contact with the evidence at issue, had established each applicant’s membership of the armed terrorist organisation on an individual basis following a careful assessment of all the elements in their specific case files.

8.  The Court notes that the applicants’ complaint under Article 7 is not manifestly ill-founded within the meaning of Article 35 § 3 (a) of the Convention or inadmissible on any other grounds. It must therefore be declared admissible.

9.  As regards the merits, the Court indeed observes that the evidence in respect of some of the applicants included material that was not at issue in Yüksel Yalçınkaya (cited above). That being said, having examined all the material and arguments submitted to it, the Court finds no reason in the present case to depart from its findings in Yüksel Yalçınkaya (cited above, §§ 237-72), for the reasons set out in detail in Demirhan and Others (cited above, §§ 35-47).

10.  It notes in this connection that the finding of violations of Articles 7 and 6 § 1 of the Convention in Yüksel Yalçınkaya (cited above) had resulted notably from the domestic courts’ characterisation of the use of ByLock, according to which anyone whose use of ByLock was established could be convicted on that sole basis of membership of an armed terrorist organisation pursuant to Article 314 § 2 of the Criminal Code (ibid., §§ 364, 413 and 414). It therefore follows, as also underlined in Yüksel Yalçınkaya (cited above, § 414), and subsequently reiterated in Demirhan and Others (cited above, § 38) that the situation that led to a finding of a violation of Articles 7 and 6 § 1 of the Convention in that case was not prompted by an isolated incident or attributable to the particular turn of events specific to the facts of that case, but potentially applied to everyone convicted for membership of the FETÖ/PDY on the basis of their use of ByLock.

11.  The Court does not rule out that there may be other evidence in respect of some of the applicants, other than their use of ByLock, that may demonstrate their organic link with the FETÖ/PDY based on the continuity, diversity and intensity of their activities and their submission to its hierarchy as required under the Court of Cassation’s case-law (see Yüksel Yalçınkaya, cited above, § 184) and thus secure their conviction as charged. The fact nevertheless remains that the establishment of the mere use of ByLock served, on its own, as conclusive proof of the presence of all of the constituent elements of the crime of membership of an armed terrorist organisation as defined in domestic law. The Court has declared this approach of the domestic courts, which effectively imputed objective liability to the users of ByLock, to be in contravention of the principle of legality safeguarded under Article 7 of the Convention (ibid., §§ 271 and 272), and it sees no reason to find otherwise in the present case (see also Demirhan and Others, cited above, § 39).

12.  In view of the above considerations, the Court concludes that there has been a violation of Article 7 of the Convention on the facts of the present case (see also Yüksel Yalçınkaya, cited above, § 272, and Demirhan and Others, cited above, §§ 39 and 46).

2. Alleged violation of Article 6 § 1 of the Convention

13.  Some of the applicants also complained that their trial and convictions for membership of the FETÖ/PDY had violated the right to a fair trial under Article 6 § 1 of the Convention, primarily for the reasons set out in Demirhan and Others (cited above, § 29). The Government argued that those complaints had not been duly raised before the Constitutional Court, either expressly or in substance, and that they should therefore be rejected for non-exhaustion of domestic remedies.

14.  The Court reiterates that the main problems identified by the Grand Chamber in this group of cases in Yüksel Yalçınkaya (cited above), and subsequently reaffirmed in Demirhan and Others (cited above), was not attributable to the particular turn of events or procedural issues specific to those cases, but resulted notably from the domestic courts’ characterisation of the use of ByLock and the uniform and global approach adopted by the Turkish judiciary vis-à-vis the ByLock evidence (see Yüksel Yalçınkaya, cited above, §§ 364, 413 and 414, and Demirhan and Others, cited above, §§ 37, 38 and 42). Having already found that this approach amounted to a violation of Article 7 of the Convention in the present case (see paragraph 12 above), which will enable the applicants to seek the reopening of the domestic proceedings in the light of the principles enunciated in Yüksel Yalçınkaya (cited above, §§ 411, 412 and 425; see also paragraph 17 below), the Court does not deem it necessary to examine whether the Government’s preliminary objection under this head may be upheld in respect of each individual application concerned.

15.  Accordingly, the Court decides not to examine separately the admissibility and merits of the Article 6 § 1 complaints raised by some of the applicants.

3. OTHER ALLEGED VIOLATIONS OF THE CONVENTION

16.  The Court notes that some of the applicants also lodged complaints under other provisions of the Convention, such as Articles 5, 8, 9, 10, 11 and 14, or raised complaints relating to other aspects of Article 6 (as in Yüksel Yalçınkaya, cited above, §§ 357, 358, 368 and 374). However, having regard to the finding of a violation of Article 7 above (see paragraph 12), the reasons for that finding (see paragraphs 10 and 11) and the specific circumstances of the case, the Court considers that it has dealt with the main legal question raised by the case and that there is no need to address the admissibility and merits of any remaining complaints (see, mutatis mutandis, Yüksel Yalçınkaya, cited above, §§ 365, 367 and 373; Turan and Others v. Turkey, nos. 75805/16 and 426 others, § 98, 23 November 2021; and Demirhan and Others, cited above, § 48).

APPLICATION OF ARTICLE 41 OF THE CONVENTION

17.  The Court considers, for the reasons explained in Yüksel Yalçınkaya (cited above, §§ 404, 411, 412 and 425; see also Demirhan and Others, cited above, § 53), that the finding of a violation of Article 7 of the Convention can be regarded as sufficient just satisfaction in respect of any non-pecuniary damage sustained by the applicants in the present case. It notes in this regard that the applicants have the possibility under Article 311 § 1 (f) of the Code of Criminal Procedure to have the domestic proceedings reopened following the delivery of the present judgment (see Yüksel Yalçınkaya, cited above, § 411), and that the reopening of the proceedings in a manner compatible with the “conclusions and spirit” of the judgment would in principle constitute the most appropriate form of redress, should they so request.

18.  Furthermore, for the reasons set out in Demirhan and Others (cited above, §§ 54-56), the Court makes no awards for costs and expenses in respect of follow-up applications of this type.

FOR THESE REASONS, THE COURT, UNANIMOUSLY,

1. Decides to join the applications;
2. Declares the applicants’ complaint that their convictions for membership of the FETÖ/PDY had violated the principle of no punishment without law under Article 7 of the Convention admissible;
3. Holds that there has been a violation of Article 7 of the Convention;
4. Holds that there is no need to examine the admissibility and merits of the applicants’ remaining complaints;
5. Holds that the finding of a violation constitutes in itself sufficient just satisfaction for any non-pecuniary damage sustained by the applicants;
6. Dismisses the remainder of any claim made by the applicants for just satisfaction.

Done in English, and notified in writing on 16 December 2025, pursuant to Rule 77 §§ 2 and 3 of the Rules of Court.

 Dorothee von Arnim Jovan Ilievski
 Deputy Registrar President

APPENDIX

List of cases: