A lawyer has begun trying to force Oreo cookies - one of the most popular biscuits in America - off the shelves in America's most populous state.
British-born attorney Stephen Joseph says an ingredient in the sandwich biscuits can damage people's health in ways little understood by the general public.
The ingredient, hydrogenated vegetable oil - also known as trans fat - has been the subject of warnings by the US National Academy of Sciences and Food and Drug Administration (FDA).
Kraft Foods, which makes the biscuit, says the suit is baseless.
Trans fats are placed into food to increase shelf life, but they decrease human life
But Mr Joseph argues that trans fats "reduce human life".
"Trans fats cause significant and serious lowering of HDL (good) cholesterol and a significant and serious increase in LDL (bad) cholesterol; major clogging of arteries; type 2 diabetes; and other serious health problems.
"Trans fats are placed into food to increase shelf life, but they decrease human life," his website, BanTransFats, claims.
Mr Joseph filed suit in California under a law that makes manufacturers responsible for products if they are not "known to be unsafe by the ordinary consumer".
'No amount safe'
The National Academy of Sciences said last year that "no amount of trans fat was safe".
The FDA urges Americans to consume as little trans fat as possible.
You can make a cookie without trans fat but what you're trading off is the unique taste and texture that people have come to expect
Kraft senior vice-president
There are no regulations requiring food manufacturers to draw attention to trans fat in their products.
It is present in untold numbers of processed foodstuffs.
Mr Joseph says he hopes to force manufacturers to switch to other types of fat.
Frito-Lay, a leading US crisp manufacturer owned by PepsiCo, announced last year that it was switching to corn oil.
McDonald's is reducing the amount of trans fat in its products by nearly half, it has said.
A senior official at Kraft said the company is "exploring ways to reduce trans fat in Oreos".
But Michael Mudd, Kraft senior vice-president for corporate affairs, told the Reuters news agency that changing the recipe would affect the flavour of the biscuits.
"You can make a cookie without trans fat but what you're trading off is the unique taste and texture that people have come to expect," he said.
The company says it has sold more than 450 billion Oreos since they were introduced in 1912.
Kraft's parent company, Altria Group, is very familiar with lawsuits alleging that its products are unsafe.
Altria owns cigarette manufacturer Philip Morris USA, the subject of many such suits.