Kristin CAVALLARI tries to keep BARRON HILTON on the STRAIGHT and NARROW!

BARRON Hilton was arrested for drinking and driving in February - but it’s not stopping Paris Hilton’s 19-year-old brother from having a good time. He showed up at Dune in Southampton the other day sporting a fake ID and was at first turned away - by Kristin Cavallari. The former “Laguna Beach” reality mess was “working the door just for fun,” said our spy. “When Barron came up she said, ‘You can’t come in here, you’re 19.’ But then a security guard let him in.” A rep for Dune said, “We don’t condone underage drinking and strictly enforce the rules.”