Warner Bros. put “Theory” into action Monday night with the Westwood premiere of the Joel Silver/Richard Donner-produced “Conspiracy Theory.”Screaming fans lined up behind the barricades to watch guests pour into the Village and Bruin theaters. After the screenings, about 600 guests motored over to Jerry’s Deli in West Hollywood, eating pasta, pizza, sushi, sandwiches and Chinese food — and all the Jerry’s baked goods you could ask for — while outtakes of the film played on monitors around the restaurant. Repping the film were Silver, director Donner, stars Mel Gibson, Julia Roberts and Cylk Cozart, and co-producers Dan Cracchiolo, J. Mills Goodloe and Rick Solomon. Also involved in the “Conspiracy” fete were WB execs Bob Daly and Terry Semel, producer Alan Ladd Jr., and thesps Christine Baranski, James Coburn, Jodie Foster, Ashley Judd, Penny Marshall, Victoria Principal, Steven Seagal, Patrick Swayze and Mario Van Peebles.