Being governed by what has happened before. If you deviate from your policies in certain circumstances, or act in a particular way on more than one occasion, then you run the risk of setting a precedent that would need to be followed in any future such occurrences. For example, having a policy stating that emergency time off is unpaid, but in reality not adjusting the payroll to deduct these hours, could set the precedent that emergency time off for dependents should always be paid!