Platinum members can normally be banned just like anybody else, but this particular one belongs to a friend of a ddoser who blackmailed Garena to gain access to a league admin account, which means he can get himself unbanned as much as he wants, not to mention banning him or his friends might aggrevate him so that he decides to compromise our business by banning/unbanning random users or even us the moderators.
Though I believe this league admin isn't very much fond of DotA hacks. I shall see what he has to say about this.