The Grand Chamber judgment of the ECtHR in Yüksel Yalçınkaya v. Türkiye was the first deci-sion to call into question, on such a scale, the legal basis of the convictions for membership of an organisation handed down after 15 July. The ECtHR held that deriving all the constituent ele-ments of the offence from the use of ByLock breached the principle of legality in criminal law, and that the defence's inability to challenge this evidence breached the right to a fair trial.