The rapid proliferation of AI-mediated digital afterlife technologies, from chatbots trained on personal data to voice clones and posthumous avatars, has generated a substantial body of ethical literature identifying the moral risks of posthumous simulation. Yet this growing consensus has not been matched by frameworks capable of translating ethical principles into operational design constraints. This paper addresses that gap from the perspective of ethical design and governance. We introduce a nine-dimensional taxonomy of digital afterlife technologies, mapping the features that carry independent moral weight in any such system: timing, consent, data sources, interaction modality, fidelity and disclosure, purpose, audience and access, governance and ownership, and autonomy and behavioral agency. Building on this taxonomy, we derive a two-tier structure of design constraints: three threshold constraints — consent, fidelity/disclosure, and purpose — that function as near-absolute conditions of permissibility (Tier 1), and six contextual dimensions that modulate ethical risk profiles without individually determining permissibility (Tier 2). A system that fails any single Tier 1 constraint is impermissible regardless of its Tier 2 configuration. We argue that the ethical constraints derived from the taxonomy are not merely evaluative, but auditable, regulatable, and actionable by designers, governance actors, and legislators. By locating normative assessment at the level of design configuration rather than stated intent alone, the framework offers a concrete bridge between existing ethical consensus and the governance of AI-mediated digital afterlives.
