if somebody tried raiding me, I would check to see if they violated their alliance's charter, first and foremost. since there is truly no international law, it means we must defer to the individual alliance laws for guidance. depending on if he had violated his or not, I would ask reps or strike back with a full force attack, as well as spy ops and a naval assault, then offer peace. I am in agreeance that there is not "right to reps", with the exception that if the raider is in violation of his/her alliances charter. If I were unaligned, I wouldn't dream of getting reps and would proceed straight to retaliation and contact the higher ups in their alliance about their actions and ask that they let me have some fun with the raider and not to interfere for the duration of the war cycle.
the question of reps lies on the rules of the alliances in question, and alliances must be plural here.
Edit: to actually answer the question, if you caused more damage fighting back than you were dealt, then yes.