As written, the law will apply to the sale of shell eggs, veal and pork. It will prohibit the sale of these goods in the state if they come from animals that were confined in ways that kept them from lying down, standing up, fully extending their limbs, or turning around freely.

There are some exclusions for foods like pizzas, soups and sandwiches that include veal or pork products.

The law is set to go fully into effect on Jan. 1, 2022.

California’s laws set similar standards for hens that produce eggs sold in the state. They took effect in 2015 and have withstood challenges in lower federal courts, including one brought in 2014 by Missouri that other states involved in Supreme Court action later joined.

The attorneys general behind the current cases suggest the California and Massachusetts laws run afoul of federal law and are in violation of the U.S. Constitution’s Commerce Clause, which prohibits state laws that discriminate against, or significantly impede interstate commerce.

A brief filed by Hawley’s office says “California is disregarding federal law by imposing novel standards on agricultural production in other States, inflating prices for consumers nationwide,” and it argues the state’s egg laws are violating the federal Egg Products Inspection Act.

One of Hill’s filings contends that, in Massachusetts, “The Animal Law nominally targets in-state retail sales, but in effect regulates animal housing in other States.”

“If the Court does not intervene,” another brief from Hill’s office adds, the law “will require compliance by livestock farmers across the country on pain of losing access to the Massachusetts market.”

The other attorneys general seeking to challenge the California statute were from Alabama, Arkansas, Indiana, Iowa, Louisiana, Nebraska, Nevada, North Dakota, Oklahoma, Texas, Utah and Wisconsin.

Those involved in the effort against the Massachusetts law were from mostly the same states. But South Carolina and West Virginia’s attorneys general also took part and Nevada and Iowa’s attorneys general did not. Except for Iowa’s Tom Miller, who is a Democrat, the rest of the attorneys general pursuing the cases were Republicans.

Massachusetts and California in their briefs cast doubt on the standing the states had to bring the cases against their laws, posited that the dispute did not warrant the Supreme Court exercising original jurisdiction, and argued the Commerce Clause claims lacked merit.

Similarly, the Trump Administration urged the Supreme Court to deny the motions by the states to proceed with the cases.