In 2014, Missouri's then-attorney general, Democrat Chris Koster, filed a lawsuit claiming the law "violated the commerce clause of the U.S. Constitution and encroaches on Missouri sovereignty," notes the Springfield Business Journal. Last year the Ninth Circuit Court of Appeals said the states "lacked the standing to pursue the claims." Current Attorney General Josh Hawley, a Republican, argued in new filings this week that "the Constitution gives states the right to defend its residents against out-of-state regulations."
Hawley told reporters, “The Constitution doesn’t allow California to regulate Missouri and we’re going to the Supreme Court to stop it. So if California is able to get by with this regulation. If they’re able to tell Missouri and other states what to do, rest assured that other states—usually big government, liberal states—will try the same sort of thing and that’s why we have to fight now.”