This chapter provides a comprehensive taxonomy of de jure defects, which are flaws in the justification or rationality of a belief as distinct from truth. These defects can be internal to an agent’s reasoning or external (e.g., failing to surmount a burden of proof, or failing to offset moral risk). The notion of weak justification is explored. There are four conditions for satisfying weak justification. Other defects include: Inference-defects which occur when a justification does not adequately support its conclusion, often involving circularity or unargued background assumptions. Inquiry-defects challenge the reliability of one’s cognitive faculties or processing of moral information, with peer disagreement serving as a significant higher-order defeater. Finally, external defects include failing to meet a burden of proof (e.g., challenging the presumption against killing innocent persons) and failing to address moral risk, which assesses the gravity of harm if one’s belief about a permissible action proves wrong. These concepts establish the framework for evaluating arguments for and against killing.