The Judgment
On 5 May 2026, the Grand Chamber of the European Court of Human Rights delivered its long-awaited judgment in Yasak v. Türkiye (Application No. 17389/20). By 11 votes to six, the Court found a violation of Article 7 of the Convention, which prohibits punishment without law, and by nine votes to eight, a violation of Article 3, which bans inhuman or degrading treatment — reversing an earlier Chamber judgment of August 2024 that had found no violation.
The case concerns Şaban Yasak, a Turkish national convicted in 2018 under Article 314 of the Turkish Penal Code of membership in an armed terrorist organization over alleged links to the Gülen movement — one of tens of thousands arrested in Turkey in the aftermath of the failed coup of 15 July 2016. He was sentenced to seven and a half years in prison. Turkish courts relied primarily on evidence of his earlier work in the movement’s education network and his membership of two associations allegedly affiliated with the movement.
In its Grand Chamber judgment, the Court held that Turkish courts had failed to show that Yasak’s earlier work in the movement’s education network, years before Turkish authorities designated it a terrorist organization, proved he knew of its alleged terrorist nature and aims or had intentionally joined and actively supported it. The Grand Chamber found that Turkish courts had focused mainly on Yasak’s alleged role in the movement’s education network but failed to show that he had any direct link to its leadership or strategic branches, knew of any allegedly terrorist aims, or had responsibilities that would prove intentional membership in a terrorist organization. The Court was unequivocal: mere involvement in a structure that was perceived at the time as a religious group could not, on its own, justify the conclusion that Yasak had the intent required for conviction of membership in a terrorist organization.
The judgment reverses what had become a deeply controversial ruling. The 2024 Chamber judgment had been criticized by lawyers and rights observers as difficult to reconcile with the Grand Chamber’s 2023 judgment in Yüksel Yalçınkaya v. Türkiye, and was subsequently named the “Worst Judgment of 2024” in the annual readers poll of the legal commentary website Strasbourg Observers.
The ECBA’s Intervention
The European Criminal Bar Association had submitted written observations as third-party intervener in Yasak, pursuant to leave granted by the President of the Court under Article 36 § 2 of the Convention and Rule 44 § 3 of the Rules of Court. The observations were submitted on 17 February 2025 by ECBA Chair Vânia Costa Ramos and Human Rights Officer Alexis Anagnostakis, with rapporteurs Cristiana Bianco, Nicola Canestrini, and Amedeo Barletta.
The ECBA’s observations identified three issues as central to the Court’s determination — all of which the Grand Chamber’s judgment has now addressed directly.
First: the principle of non-retroactivity. The ECBA argued that criminal liability cannot attach to conduct that was lawful at the time it occurred. The mere fact that an organization is subsequently designated as terrorist does not, without more, render prior membership criminal. Foreseeability must be assessed from the perspective of the individual at the time of the acts — not with the benefit of hindsight and not by reference to a designation that did not yet exist. The Grand Chamber’s finding that Turkish courts failed to individualize their assessment of what Yasak knew and when he knew it reflects precisely this principle.
Second: the requirement of individual culpability. The ECBA emphasized that conviction for membership in a terrorist organization requires proof of both actus reus and mens rea. Participation in activities that carry a presumption of legality — working in an educational network, membership of associations, attendance at community gatherings — cannot substitute for concrete evidence of the accused’s actual knowledge of the organization’s criminal nature. The Grand Chamber’s refusal to accept Yasak’s educational activities as sufficient proof of intentional terrorist membership vindicates this position.
Third: the use of prima facie lawful conduct as evidence. The ECBA warned against the criminalization of conduct that was, at the relevant time, entirely lawful and indeed socially endorsed. Temporal context, the observations argued, is indispensable to any assessment of whether ostensibly legitimate activities can constitute evidence of terrorist affiliation. The Grand Chamber’s emphasis on the temporal gap between Yasak’s conduct and the movement’s eventual designation as terrorist reflects exactly this concern.
Significance of the Judgment
The Grand Chamber’s judgment in Yasak is significant on several levels.
It consolidates the jurisprudential foundations laid by Yüksel Yalçınkaya v. Türkiye (2023) and places beyond doubt that the fundamental safeguards of Article 7 — accessibility, foreseeability, legal certainty, and individual culpability — apply with full force in terrorism-related prosecutions. States cannot, under cover of counter-terrorism, convict individuals for conduct that was lawful when it occurred and could not reasonably have been understood as criminal at that time.
The judgment also carries systemic significance for the tens of thousands of individuals in Turkey who have been prosecuted and convicted in connection with the Gülen movement in the aftermath of the 2016 coup attempt. The principles affirmed by the Grand Chamber — that mere association with a lawful organization cannot suffice for a terrorism conviction, and that individualized proof of knowledge and intent is required — will need to be applied by domestic courts in the review and retrial of those cases.
More broadly, the judgment speaks to a question that arises across all Council of Europe member states: as counter-terrorism legislation continues to expand, and as the definitions of terrorist affiliation and support grow ever wider, what limits does the Convention impose? The Grand Chamber’s answer is clear. Article 7 is not a procedural formality. It is a substantive guarantee that the state must prove, individually and concretely, that an accused person knew what they were doing was criminal — at the time they did it.
Conclusion
The ECBA intervenes before the European Court of Human Rights when cases raise questions of systemic importance to the rights of the defence across Europe. Yasak v. Türkiye was precisely such a case. The Grand Chamber’s judgment — affirming the principles the ECBA advanced in its written observations — demonstrates the value of that institutional role.
The nullum crimen, nulla poena sine lege principle is the bedrock of criminal justice. It means that the state cannot punish a person for conduct that the law did not prohibit at the time it was committed. Today’s judgment reaffirms it. The ECBA will continue to defend it — in Strasbourg, and wherever the rights of the defence are at stake.