Should restaurants have to provide an ingredients list when asked?

Other than rush hour traffic (sigh), I love living in my busy little community of West Los Angeles. Located near Sawtelle Ave. and Olympic Blvd., the area I live in is a "Little Tokyo" area of sorts. There are many sushi, noodle houses and kushiyaki restaurants, artsy boutiques, a cool little Japanese coffee place where they roast their beans in-house, and a touristy knick-knack store with oodles of Hello Kitty goodies.  Normally when my digestive and immune system aren't failing me (like it currently is) I'd be slurping up a bowl of soba noodles or eating some beef satay. But sadly, many private eateries will not divulge their ingredients, even to someone like me who has a dietary reason. Others are just not knowledgable in dietary needs.