Sanctions and export control regimes attach consequences to knowledge, including the “knowledge” a party would have had but for a deliberate decision not to ask. Declining to verify an end user, or accepting an explanation that the surrounding facts contradict, does not create a defence.
Enforcement narratives typically establish it through the trail of unanswered questions: the internal email raising a concern, the check that was started and abandoned, the escalation that was closed without a reason.