If a Milosevic knew with reasonable certainty that ethnic cleansing would be prevented and punished, he might not attempt it.
Milosevics have never even considered engaging in ethnic cleansing. 
mnli hypothesis: Milosevics have never even considered engaging in ethnic cleansing.  premise: If a Milosevic knew with reasonable certainty that ethnic cleansing would be prevented and punished, he might not attempt it.