I'm in agreement with biker yet again lol (hey Biker--gives the infamous nod). Toneus, "non-consensual" inherently means no consent...which in the eyes of the law is never justifiable.
I think what you were really asking was since the ler typically doesn't enjoy being the lee, if the lee was able to overpower the ler and have his or her revenge, would that be considered okay even though technically the person will not be "enjoying" it. The question really comes down to if the act is done in a joking or playful way. If the ler who became the lee is seriously saying stop or freaking out, that's not cool. If the person is hating it but at the same time okay with it as a revenge thing....it should be pretty clear. If you find yourself in a situation where you can't tell the difference between playful actions violating someone...always be on the safe side and err on the side of caution (meaning either get their consent or don't move forward).