Rules and Justice

Last Thursday, I applied the final test of microprocessors to my students. One student missed it, but he asked me to apply another test for him. He just decided not to show at the final test.
During the microprocessor course, the students were divided in groups. He was always making other stuff, pretending he was working with his colleagues. I know he does not deserve the score I assigned to his group.
What is justice?
A person is seen as correct when follows the rules, but is it enough?
Depending on how I follow the rules, this lazy student will pass without studying. A professor makes justice when he pass students that learned the subject and reproves otherwise. This is a little different of following rules because a student can be benefited by group works. In general, rules work very well and the score assigned to the student is fair, but there are exceptions. Perhaps, the rules should be refined for these special cases. The problem is that more rules creates other cracks in the approval requirements and it must be impossible to create the perfect set of rules.
Justice can not be accomplished by a set of rules. It is beyond that.