lockecole said:
If somebody (John) hurted somebody else (Mary) breaking the law and John can not be punished by anybody in any way other than Mary hurting John breaking the law too, should Mary still punish John?
One way I could see this situation as potential is if John and Mary are the only two on an island, and they have reached an agreement (i.e, a law) not to "initiate" force against one another (the nose example by Arildno). So, let us consider the morality of the situation you ask. As you can clearly see, it is only John that is a law breaker in your example at the present time, not Mary, because Mary does not "initiate" force.
Now, to the question, "should Mary punish John" in future time? Clearly, Mary had the moral right to "defend" herself in past time, when John was trying to hurt her, but that is not what you ask, you ask if Mary should hurt John back as a way to punish in future time. For me, the correct moral answer is
no because then it would be Mary that has initiated force in future time, with the motive to "punish", as opposed to the initial motive of John in past time, which was to "hurt".
Now, does this mean that Mary should not "punish" at all. No, Mary has a moral obligation to punish in order to teach John that laws are important if the two are to coexist on the island. But now is the question, can one punish without hurting ? I think so, consider the time-out chair for children that misbehave. It is meant to teach, not to hurt. Must one always punish without hurting ? No, there are some examples of humans hurting by initiating force against other humans that result in loss of life (which are not self-defense), in such cases it would be morally correct for "society" to take the life of the person that initiated the loss of first life, for the simple reason that the only "single" person that would have such a right is now dead.
In conclusion, to answer your question, "should Mary punish John"--I hold that the correct moral answer is yes, but never by physically and/or mentally hurting John, only to the extent that John is taught a moral lesson. Now if John has lust after Mary, we can see a clear path for Mary to take as punishment that should also teach a lasting lesson.