In 2017 Iowa enacted a law that provides significant protections for animal feeding operations in the area of nuisance law. It's Iowa Code 657.11, entitled "Animal Feeding Operations." It includes in the concept of "animal feeding operation" a broad array of agricultural activities: "[A] lot, yard, corral, building, or other area in which animals are confined and fed and maintained for forty-five days or more in any twelve-month period, and all structures used for the storage of manure from animals in the operation.
Iowa Code 657.11's stated purpose "is to protect animal agricultural producers who manage their operations according to state and federal requirements from the costs of defending nuisance suits, which negatively impact upon Iowa’s competitive economic position and discourage persons from entering into animal agricultural production. This section is intended to promote the expansion of animal agriculture in this state by protecting persons engaged in the care and feeding of animals." In other words, Iowa doesn't want agricultural producers being sued for a nuisance related to dust, noise, odors, or other emanating from their operations unless the operation's being run really irresponsibly.
That stated purpose represents a major departure from Iowa's standard nuisance law. The general rule is that compliance with regulations and laws is not a defense to a nuisance lawsuit. Agricultural producers now enjoy an argument that's usually not available for other types of defendants in a nuisance case.
To advance Iowa Code 657.11's stated policy, it creates a qualified immunity from nuisance suits for animal feeding operations: "An animal feeding operation . . . shall not be found to be a public or private nuisance under this chapter or under principles of common law, and the animal feeding operation shall not be found to interfere with another person’s comfortable use and enjoyment of the person’s life or property under any other cause of action." A nuisance plaintiff can only overcome that immunity and proceed with suit if the plaintiff proves that (1) the agricultural producer has failed to comply with a federal statute or regulation or a state statute or rule that applies to the animal feeding operation or (2) the animal feeding operation unreasonably and for substantial periods of time interferes with the person’s comfortable use and enjoyment of the person’s life or property and the animal feeding operation failed to use existing prudent generally accepted management practices reasonable for the operation.
The qualified immunity provisions are another significant departure from Iowa's usual nuisance laws to the extent that they allow a "state of the art" defense, i.e., an argument that the animal feeding operation uses "existing prudent generally accepted management practices reasonable for the operation." In other types of nuisance claims, the defendant's reasonable care, use of technology, etc. is not a defense. A defendant can normally be found liable for causing a nuisance despite the defendant's best efforts to prevent it. Yet animal feeding operations can escape nuisance liability, even if they're truly causing a nuisance, as long as they can prove that they're doing the best they can to prevent the nuisance.
Iowa Code 657.11 makes another change to standard nuisance law for animal feeding operations with its provision that the qualified immunity applies "regardless of the established date of operation or expansion of the animal feeding operation." Usually the chronology of events is important in a nuisance case. If the person suing for a nuisance was using the property before the nuisance-causing activity began, that's normally a major advantage for the plaintiff in the case because, in essence, they were their first and have priority. But Iowa Code 657.11 eliminates that advantage by allowing the qualified immunity regardless of whether the complaining landowner had priority of use.