After a bruising campaign last fall, Californians voted by a 27-point margin in favor of what was billed as an effective ban on cages for egg-laying hens.

The Humane Society of the United States, which sponsored the measure, may have won that battle. But the war over Proposition 2, it seems, is just getting started.

The egg industry says the proposition might allow it to use cages, and wants an interpretation from the state to support that idea. The Humane Society isn't budging. It says voters meant to enact a ban on cages, and that's what they should get.

Meanwhile, the fighting has moved to other fronts.

The society is backing Assembly Bill 1437, which would require all eggs sold in the state – not just those laid in the state – to comply with the ballot measure. And it has organized a sweeping class-action suit alleging massive price-fixing by egg farmers.

The University of California, hoping to insert itself as a peacemaker, formed a new animal welfare council last month. But at the same time, the university is being sued by the Humane Society over what the group says was an industry-biased analysis of Proposition 2 during the campaign.

While the Humane Society presses its advantage, the egg industry is seeking to find some leverage of its own in the language of the proposition.

While billed as a ban on the wire boxes that house most of California's egg-laying hens, Proposition 2 doesn't explicitly prohibit cages.

"It doesn't say anything is specifically allowed or prohibited," said Fiona Hutton, spokeswoman for the Association of California Egg Farmers.

Instead, it guarantees hens the space for some basic behaviors, including extending their wings – which average 28 inches, tip to tip – without touching another bird or the side of a cage. That's not possible in today's standard cages, in which eight hens typically share a 4-square-foot cage.

Egg farmers say they intend to comply with Proposition 2's standards. But they also say there's more than one way to do that.

One option, Hutton said, might be the 60-hen "colony" cages in use on some farms in Europe, where each bird gets about 1 square foot of space, and access to amenities like perches and nesting boxes.

"There are a number of different enclosure options we could discuss and negotiate on," she said. The industry is hoping the Legislature will clarify what sorts of housing will be allowed.

The Humane Society, however, says the measure is clear.

"It's a de facto ban on cages," said Paul Shapiro, senior director of the Humane Society's factory farming campaign.

"Technically, you could have one bird in an extremely large cage," Shapiro said. But it would be simpler – and more economical, he says – to switch to standard cage-free production, where thousands of hens share an open barn with an average of at least 1.5 square feet apiece.

Whatever the outcome, the impact on retail egg prices is likely to be modest. Several studies have found that egg production costs in a cage-free barn are about 20 percent higher – roughly 1 cent per egg – than in a barn fitted with standard cages. The cost of producing an egg in the European-style colony cages is somewhere in between.

Retail prices for cage-free eggs are typically $1 to $2 higher per dozen than for standard eggs, exaggerating the difference in production costs. If only cage-free eggs were available in stores, much of that mark-up would likely vanish, said Daniel Sumner, an economist at the University of California, Davis.

If the Legislature passes hen-housing specifications that the Humane Society opposes, the group will likely have a good chance of overturning it in court, said Mary-Beth Moylan, an election-law expert at McGeorge School of Law in Sacramento.

Courts tend to be skeptical of legislative attempts to "clarify" the language of a ballot measure, Moylan said. In addition, she said, the egg industry's case wouldn't be helped by its statements in the Official Voter Information Guide, which said the measure would not only effectively ban standard cages, but also force farmers to let their hens roam outside for most of the day.

Defending its interpretation of Proposition 2 is critical to the Humane Society's national strategy. In addition to backing AB 1437, the group is supporting bills with language virtually identical to Proposition 2 in two other states, and is planning a ballot measure in Ohio.

Aggressive litigation is part of that strategy.

The group has sued the University of California over an analysis of Proposition 2 published by a group of researchers last July. Cited widely in newspaper articles during the campaign, the report concluded – among other things – that the ballot measure would effectively kill the California egg industry.

The Humane Society wants the university to turn over all documents concerning the preparation of the report, contending that some may show that the egg industry improperly influenced the authors. The case, being heard in Woodland, is in its early stages.

Humane Society lawyers also helped launch a sweeping class-action suit filed last year that targets virtually the entire U.S. egg industry, including prominent California producers. The plaintiffs, mainly companies that buy eggs, allege the egg industry has for years colluded to limit production, raising prices and boosting their profits by what amounts to billions of dollars.

A spokesman for the United Egg Producers, the leading national egg-industry group, called it "a nuisance lawsuit without any merit whatsoever."

Last week, however, one of the defendants, a large Minnesota egg operation, agreed to settle, court documents show.

The Humane Society hopes to use the price-fixing case to counter the industry's argument that switching to cage-free production will hurt consumers by driving up prices, said Peter Brandt, one of the group's attorneys.

Call The Bee's Jim Downing, (916) 321-1065.