ORLANDONBA commissioner David Stern interrupted the halftime ceremony of the Sixers-Magic game Wednesday to announce that Shaquille O'Neal would be returning to the court this postseason, not as a player, but as a guest referee in Game 1 of the Eastern Conference Championship. 'It's time I brought the law enforcement back into the NBA,' Stern said as he introduced the unsmiling O'Neal, who glowered at the crowd while wearing a black-and-white-striped referee shirt with the sleeves cut off. 'He won't let any of you get away with the crap you're pulling with the current refs. Shaq Attack is backand in full effect.' In addition to O'Neal, Stern has appointed Vince Carter to serve as 'The Enforcer,' whose job is to check tickets and sell concessions at all games. 