A proposal that would ban modern housing systems for egg-laying hens, veal calves and gestating sows by 2015 was approved Tuesday by California voters.

Florida, Arizona, Colorado and Oregon have passed similar laws for swine and veal.  California, however, becomes the first state to require that all egg-producing chickens be kept in more spacious enclosures or free to roam a henhouse. Most pig and veal farmers in the state have already expanded their pen sizes. As a result, the law's requirements will have the most significant impact on poultry farmers.

Supporters of Proposition 2 said the initiative would guarantee farm animals a better life, giving them the space they need to stand up, turn around, lie down and extend their wings, as well as prevent diseases caused by overcrowding.

Opponents argue that the cost of the measure threatens California's egg industry and may force California livestock and poultry operations into other states or put some out of business.

In approving the initiative, voters rejected the arguments of Gov. Arnold Schwarzenegger, the agriculture industry and the American Veterinary Medical Association (AVMA).

Debated heavily on TV, opponents said the measure would increase the price of California-raised eggs, potentially crippling a thriving industry. Backers, meanwhile, argued that farm animals deserve humane treatment and said the changes would cost consumers just a few cents per dozen eggs.