Proposition 2, passed by California voters in November 2008, requires that egg-laying hens cannot be confined in cages that prevent them from 'lying down, standing up, and fully extending his or her limbs' and from 'turning around freely', reports Courthouse News.

ACEF claims in Fresno County Court that Prop. 2 is unconstitutionally vague and does not let farmers know how to confine hens so as to avoid criminal punishment and fines.

"Proposition 2 clearly attempts to place some restrictions on size and density of the enclosures that California commercial egg farmers may use to house their egg-laying hens. However, Proposition 2 provides no ascertainable guidance on the required dimension or densities of hen enclosures; it merely requires that each hen not be prevented from performing required behaviors for all or the majority of the day," the complaint states.

California egg farmers must comply with Prop. 2 by 1 January 2015 or face imprisonment of up to 180 days and fines of up to $1,000 per violation.

The Association claims that enclosures used by most commercial egg farmers in California do not meet Prop. 2's requirement, and that most housing systems for more than 19 million egg-laying hens on commercial egg farms in the state will have to be replaced or remodeled in the next two years.

"ACEF estimates that this will cost more than $400 million. Yet, due to the inherent vagueness of Proposition 2, ACEF's members lack sufficient understanding of how to revamp their hen enclosures to comply with Proposition 2. This uncertainty makes it untenable for ACEF's members to arrange financing and to invest the millions of dollars that it will take to comply with Proposition 2 by Jan. 1, 2015," the complaint states.

To avoid the risk of criminal prosecution, fines, and wasting money on nonconforming containers, many egg farmers will shut down, forcing millions of hens to be euthanized, according to the complaint.

"The continued viability of the California egg industry is in jeopardy due to Proposition 2," the complaint states.

ACEF claims that proposed federal regulations provide specific calculations for the minimum number of square inches of floor space per hen, and would pre-empt Proposition 2.

"The proposed federal legislation is not tied to the same vague behavior-based standard that is contained in Proposition 2. Instead, it would impose specific space per hen requirements that would allow egg farmers the ability to determine what size of enclosures to build and how many hens to place in each enclosure," the complaint states.

Courthouse News reports that Prop. 2 has already faced two court challenges.

The first unsuccessfully tried to clarify the type and dimensions of housing for hens required by Prop. 2.

The second, filed by egg producer, William Cramer, challenged Prop. 2 under the US Constitution but a federal judge dismissed that case with prejudice in September.

"The court concludes that the Proposition 2 is not impermissibly vague in all of its applications, or even in a single application as argued by plaintiff," US District Judge John Walter wrote.

"Proposition 2 provides a person of ordinary intelligence more than a reasonable opportunity to know what is prohibited and provides explicit and objective standards to prevent discriminatory enforcement," he added.

Mr Cramer's claims were purely speculative and cannot outweigh California's legitimate interest in preventing animal cruelty, the judge found.

The Courthouse News report concludes that ACEF, which had tried unsuccessfully to intervene in Mr Cramer's suit, challenges Prop. 2 under the California Constitution. ACEF is represented by Dale Stern and John McCarron with Downey Brand. It wants enforcement of Prop. 2 enjoined. Named as defendants are California and Attorney General Kamala Harris.