In a casino, they only have to suspect cheating to ask you to leave. In a GM tournament I don't think the judges or sponsors could just say someone's playing be

In a casino, they only have to suspect cheating to ask you to leave. In a GM tournament I don't think the judges or sponsors could just say someone's playing better than usual and is therefore banned. There needs to be a little more evidence than a one-in-twenty win happening. Less likely things happen every day.