The US Supreme Court on Thursday preserved a California law banning the sale of pork in America's most-populous state from pigs kept in tightly confined spaces, rejecting an industry challenge claiming that the voter-backed animal welfare measure impermissibly regulates out-of-state farmers, reported Reuters.

The justices upheld a lower court's decision to dismiss a lawsuit by the National Pork Producers Council and the American Farm Bureau Federation seeking to invalidate the law. The industry had argued that the measure violated a U.S. Constitution provision called the Commerce Clause that courts have interpreted as empowering the federal government - not states - to regulate interstate commerce.

"While the Constitution addresses many weighty issues, the type of pork chops California merchants may sell is not on that list," wrote conservative Justice Neil Gorsuch, who authored the court's ruling.

The measure, approved by voters as a 2018 ballot initiative called Proposition 12, bars sales in California of pork, veal and eggs from animals whose confinement failed to meet certain minimum space requirements.

The law mandates pig confinement spaces large enough to enable the animals to turn around, lie down, stand up and extend their limbs. Animal rights groups have said some pork producers confine pigs in cages so small that pigs cannot turn around for most of their lives.

The pork industry groups argued that the law violated the Constitution by forcing farmers in other states to change their practices in order to sell pork in California, a lucrative market.

California farms collectively are only a small part of the $26 billion-a-year US pork industry. The size of cages used at American pig farms is humane and necessary for animal safety, according to the industry, which asserts that California's law gives the state unwarranted influence over the pork sector.

President Joe Biden's administration sided with the pork producers in the case, saying that states cannot ban products that pose no threat to public health or safety due to philosophical objections.

Proposition 12 set the required space for breeding pigs, or sows, at 24 square feet (2.2 square meters). The current industry standard is between 14 and 20 square feet (1.3 to 1.9 square meters), according to a 2021 report from Dutch banking and financial services company Rabobank.

The Supreme Court took up the case after the San Francisco-based 9th US Circuit Court of Appeals affirmed a judge's decision to throw out the pork industry challenge.