Autonomy without terminality: the legal threshold of “UN- bearable suffering” in EU assisted dying frameworks after mortier v. Belgium

European assisted dying statutes diverge sharply on whether an applicant must be ter- minally ill, and the divergence has consequences that the literature has not adequately theorised. Where terminality is required, eligibility turns largely on a medically verifiable predicate about the applicant's condition. Where it is not required, as in Belgium, the Netherlands, and Luxembourg, and as an implication of the German Federal Constitutional Court's 2020 ruling, the whole weight of gatekeeping falls on a predicate that only the applicant can access: unbearable suffering. This article develops the concept of the epistemic gatekeeping load, defined as the share of an eligibility determination that rests on first-personally accessible predicates, and argues that it varies inversely with terminality requirements across the European regimes. From this I derive the article's central thesis, which I call procedural substitution: as the epistemic gatekeeping load rises, legal systems do not and cannot compensate by refining the substantive definition, and instead substitute pro- cedural architecture for substantive review. Mortier v. Belgium is the moment at which the Eu- ropean Court of Human Rights made this substitution explicit at the supervisory level, holding that a permissive regime does not violate Article 2 in substance even for a non-terminal psychi- atric applicant while locating a violation in the independence of the ex post control body and the length of the criminal investigation. Karsai v. Hungary confirms the pattern from the opposite direction through a wide margin of appreciation. The article's normative claim follows: the long- running complaint that “unbearable suffering” is unacceptably vague is misdirected, since the vagueness is not a drafting defect that better definition could cure but a structural entailment of abandoning terminality, and the appropriate locus of reform is therefore the design of review institutions. The analysis is doctrinal and comparative, draws on sixty verified sources, and offers legal analysis rather than legal advice.