In a real game, they would just delete his account and block him from re-registering without any evidence of malfeasance.
I've been banned from multiplayer server networks for playing while sleep deprived. I would just react to any moving objects and headshot them while running laps around the map, or by taking extreme advantage of game mechanics. In Alien versus Predator 2, I would get banned from servers for clinging to the ceilings above doorways, and headbite people as they came though (usually a one-shot kill), or using AP ammunition with the few guns that had it, and just melt down armored classes. Didn't cheat, but apparently being any good at a game with special gameplay mechanics is impossible without cheating, right? Feh.