The Grand Chamber judgment of the ECtHR dated 5 May 2026 in the case of Yasak v. Turkey constitutes an extremely important precedent with regard to prosecutions for membership in an armed terrorist organization conducted after 15 July.
The judgment is not merely an assessment of the conviction of the individual applicant Şaban Yasak; it also establishes a strong European Convention on Human Rights standard regarding the limits within which evidence such as “association,” “connection,” “affiliation,” “past contact,” “roles within an educational structure,” “witness statements,” “Bank Asya transactions,” and “HTS records” — long debated in Turkish criminal proceedings — may be used as a basis for criminal liability.
The subject of the judgment is the applicant’s conviction for “membership in an armed terrorist organization” under Article 314/2 of the Turkish Penal Code, as well as his detention/prison conditions in Çorum Prison.
The issue before the Grand Chamber was examined primarily under two rights: the principle of “no punishment without law” guaranteed by Article 7 of the Convention and the prohibition of inhuman or degrading treatment guaranteed by Article 3 of the Convention.
The Court found, by 11 votes to 6, a violation of Article 7, and by 9 votes to 8, a violation of Article 3.
The most important aspect of this judgment is that the ECtHR clearly states that criminal liability cannot be based on “collective guilt” or “guilt by association.”
According to the Court, in allegations as serious as membership in an armed terrorist organization, it is not sufficient that a person is present in a certain environment, has contact with certain individuals, has participated in certain educational structures in the past, or is referred to by certain titles by some witnesses.
Criminal courts must demonstrate, through concrete, individualized, and context-appropriate reasoning, that the person knew the violent aims and methods of the organization, knowingly and willingly adhered to those aims, and manifested a continuous intention of membership.
In the words of the ECtHR, both the material and the mental elements of the offense must be clearly established; otherwise, punishment becomes detached from the principle of “personal culpability” and violates Article 7 of the Convention.
The Grand Chamber placed particular emphasis on mens rea, that is, the mental element of the offense.
According to the Court, under Turkish law as well, for the offense under Article 314/2 to be constituted, the person must knowingly and willingly join an armed terrorist organization, be aware of its nature and violent methods, and nevertheless maintain their connection to it.
At this point, the ECtHR also refers to the Court of Cassation’s (Yargıtay) approach of “direct intent” and states that a genuine intention of membership must not be confused with mere contact, social relations, or past religious/discussion/educational environments.
Looking at the applicant’s situation, it appears that the domestic courts relied on elements such as his alleged roles within an educational structure, witness statements associating him with titles like “BTM/BBTM,” certain connections reflected in HTS records, as well as Bank Asya transactions and social security records.
However, according to the ECtHR, the problem is not the existence of these pieces of evidence per se, but the failure of the domestic courts to explain how these elements led to the conclusion that the applicant knew the terrorist nature of the organization, adopted its violent aims, and joined it knowingly and willingly.
In other words, the ECtHR went beyond asking “Is there evidence?” and instead asked: “Do these pieces of evidence actually prove the mental element of the offense?”
In this respect, the judgment is a continuation and expanded application of the Yalçınkaya judgment.
In Yalçınkaya, the automatic attribution of guilt based on evidence such as ByLock use, Bank Asya, and union/association membership was criticized.
In Yasak, however, a conviction not centered on ByLock, but rather based on witness statements, allegations concerning educational structures, and HTS and financial/social records, was examined.
The Grand Chamber held that even with a greater diversity of evidence, the fundamental problem remains unchanged: a conviction cannot be established without individualizing all elements of the offense.
One of the strongest aspects of the judgment for legal practice is its emphasis on the “temporal element.”
The ECtHR finds that the domestic courts transformed certain activities of the applicant into grounds for punishment retroactively, based on the later classification of the structure as a terrorist organization.
However, in criminal law, what is decisive is what the person knew at the time of the alleged acts, with what intent they acted, what characteristics of the organization they were aware of, and what concrete contribution they made despite this knowledge.
The Court emphasized that a past role in the field of education, by itself, does not demonstrate a personal, functional, or hierarchical link to a strategic or violent structure.
This finding is directly relevant for a large number of cases in Turkey.
Because in many convictions, a person’s social, professional, religious, educational, or financial contacts prior to 2013 or 2016 have been used as grounds for punishment in light of later organizational characterizations.
The Yasak judgment shows that this approach raises serious issues under Article 7 of the Convention.
A court cannot automatically criminalize a person’s actions at a certain time by relying on later political, judicial, or security assessments.
Especially where a structure has existed in society for many years with different appearances and activities, criminal courts must establish personal culpability with particular care.
Another important aspect of the judgment is its approach to allegations concerning “educational” or “student” structures.
The ECtHR noted that the applicant’s role in the educational sphere was emphasized, but that no personal, functional, or hierarchical link with the organization’s strategic, operational, or violence-related branches was demonstrated.
This is an extremely strong statement for the defense.
Because merely working in an educational institution, staying in student houses, attending meetings, being referred to as a student supervisor, or having contact with certain individuals does not in itself show that a person knew and adopted the violent aims of an armed terrorist organization.
The Court made clear that criminal liability must be based on “concrete link,” “concrete knowledge,” “concrete intent,” and “concrete contribution.”
The ECtHR found that the domestic courts did not assess the applicant’s mens rea, but merely listed the evidence and then proceeded to convict.
This finding also contains a fundamental criticism applicable to many reasoned judgments in Turkey: a reasoned judgment cannot consist merely of a list of evidence.
The court must explain how each piece of evidence proves each element of the offense.
Particularly in a serious offense such as membership in an armed terrorist organization, it is not sufficient for the court to state that “the defendant had intent”; it must demonstrate through which facts, at which times, through which acts, with what level of knowledge, and with what continuity this intent was formed.
Otherwise, the conviction violates the principles of legal certainty and foreseeability.
The judgment is also significant with regard to Article 3 of the Convention.
The ECtHR assessed the conditions in Çorum Prison as a whole and concluded that factors such as overcrowded wards, inadequate toilet/shower facilities, sleeping on the floor, and sleep disruption due to artificial light and noise, taken together, exceeded the threshold of degrading treatment.
In particular, the principle of “one prisoner, one bed” was emphasized, and prison overcrowding and the prolonged duration of adverse conditions were taken into account.
However, the fact that the decision under Article 3 was adopted by 9 votes to 8 shows that there was a serious division of opinion within the Court.
Some judges did not agree with the finding of a violation, taking into account that the personal space had not always fallen below 3 m².
The majority, however, considered not only the square meter calculation but the overall impact of the conditions, including sleep quality, hygiene facilities, general overcrowding, and duration.
This approach shows that in applications concerning prison conditions, not only the space per person but the overall impact of living conditions must be documented.
As for just satisfaction, the ECtHR did not award additional non-pecuniary damages for the violation of Article 7, considering that the finding of a violation constituted sufficient just satisfaction in this respect.
However, the Court emphasized that the applicant may request reopening of the proceedings under Article 311/1-f of the Code of Criminal Procedure in domestic law, and that this constitutes the most appropriate means of redressing the Article 7 violation.
This point is highly important in practice.
Because the real consequence of the judgment is not merely a symbolic finding of a violation, but the opening of the way for retrial in domestic law and the need to reassess the conviction in line with the standards set by the ECtHR.
The ECtHR awarded the applicant 2,800 euros in non-pecuniary damages for the violation of Article 3, as well as 9,050 euros for costs and expenses.
Claims for pecuniary damages and other requests were rejected.
In conclusion, the Yasak v. Turkey judgment clearly and strongly establishes the following fundamental principle for post-15 July cases: criminal proceedings cannot be based on collective assumptions, retroactive classifications, abstract organizational narratives, or chains of association.
For a conviction, the individual’s personal culpability, criminal intent, knowledge of the organization’s violent aims, and conscious and willing participation must be concretely demonstrated.
Without this, a conviction violates the principles of legality, foreseeability, and personal culpability under Article 7 of the Convention.
General and Personal Assessment
The Grand Chamber judgment of the ECtHR dated 5 May 2026 in Yasak v. Turkey constitutes a highly significant turning point for criminal proceedings conducted after 15 July.
The Court found that the most fundamental principle of criminal law was violated in the applicant’s conviction for membership in an armed terrorist organization: a person cannot be punished without their personal culpability and criminal intent being concretely established.
At the center of this judgment lies mens rea, that is, the mental element of the offense.
According to the ECtHR, the domestic courts noted that the applicant had taken on certain roles within an educational structure in the past, that his name appeared in certain witness statements, and that there were elements such as HTS data and Bank Asya records; however, they did not explain how these elements proved that the applicant knew the organization’s violent aims, knowingly and willingly participated in them, and maintained a membership intent.
The message of the Grand Chamber is clear: a person cannot be convicted solely on the basis of past contacts, social environment, educational activities, abstract witness statements, or subsequent general organizational assessments.
Criminal liability must be based on individual and concrete culpability, not collective assumptions.
The judgment is particularly important in terms of the temporal element.
The ECtHR emphasized that what the person knew at the time of the alleged acts, with what intent they acted, and whether they were aware of the organization’s violent nature must be examined carefully.
A later classification as a terrorist organization cannot automatically render past contacts or activities criminal.
For this reason, the Yasak judgment is a continuation of Yalçınkaya but extends beyond it.
Because the issue here is not limited to ByLock or a specific digital piece of evidence.
The ECtHR stated that even where multiple forms of evidence such as witness statements, allegations of educational structures, HTS data, Bank Asya transactions, and social security records exist, a conviction still requires that the mental element be demonstrated in an individualized manner.
Another aspect of the judgment concerns prison conditions.
The ECtHR concluded that overcrowding, sleeping on the floor, inadequate hygiene, noise, and poor sleep conditions in Çorum Prison, taken together, constituted a violation of Article 3.
In conclusion, the Yasak v. Turkey judgment strongly reiterates the following legal principle for many cases in Turkey: in criminal law, the offense is proven through the individual, not through environment, relationships, past contacts, or general assumptions.
It is not sufficient to list evidence for a conviction; it must be clearly demonstrated how each piece of evidence proves the material and mental elements of the offense.
This judgment is not only a finding of violation for the defense, but also a very powerful Grand Chamber precedent that can be used in retrial requests, mens rea discussions, and challenges against unreasoned convictions.
