If a Milosevic knew with reasonable certainty that ethnic cleansing would be prevented and punished, he might not attempt it.
Some Milosevics are committed to ethnic cleansing regardless of the punishment. 
mnli hypothesis: Some Milosevics are committed to ethnic cleansing regardless of the punishment.  premise: If a Milosevic knew with reasonable certainty that ethnic cleansing would be prevented and punished, he might not attempt it.