Iowa Gov. Terry Branstad last week joined five other states in a lawsuit opposing California’s egg-production law, which he says violates the commerce clause and discriminates against Iowa’s egg producers.

The California law requires all eggs sold in the state to come from chickens raised in cages where birds have enough room to spread their wings without touching another bird. About 30 percent of the eggs imported into California are produced in Iowa.

"The burdensome law from the state of...