Although "thumbs up" or "thumbs down" can't be trademarked by Roger Ebert or anyone else, for that matter, since the gesture originated in ancient Rome, "two thumbs up" or "two thumbs down" can be, a legal expert argues. And there's the rub, according to Chicago Tribune entertainment writer Mark Caro, writing in today's (Friday) edition and quoting intellectual property expert E. Leonard Rubin. "Disney cannot use ['Two Thumbs Up']," Rubin told Caro, "but people on television during the show, I believe, are not prohibited from using a gesture thumbs-up or a gesture thumbs-down: 'I liked it,' 'I didn't like it.'"