In my opinion, the term 'leave' refers to the leave of absence from work, which means the permission to be away from work for some particular reason. Therefore, in the first place, leave cannot be claimed as a matter of right; the employee has to apply earlier and seek the prior permission of the sanctioning authority.
Of course, there are certain contingencies like small indispositions which cannot be anticipated, resulting in availing of leave for a shorter spell without prior permission. That's a rare thing to which no superior would be indifferent. But the incident like the one mentioned in the query exhibits a total disregard for authority and discipline on the part of the employee. Like Vadodara and Saikumar suggested, if it is the first such occasion, the individual may be let off with a severe warning.