Saying the issue goes far be­­yond egg production practices, Iowa lawmakers vowed last week to continue to use legal and legislative tools to overturn a California law that is designed to block sales of eggs laid in conventional cage-type housing.

Iowa lawmakers claim that the California egg law, set to take effect in January, clearly violates the commerce clause of the U.S. Constitution and is simply designed to protect California’s egg producers at the expense of those in other states. They also warn that the law, if imposed, has the potential to spark a costly trade war among states over a range of practices in livestock and grain farming, such as the use of sow...