Barr has apparently answered my question. He reportedly indicated that the DOJ would consider getting involved on behalf of businesses objecting to quarantines. The basis for this would have to be the commerce clause.
Go for it, big boy! If the litigation is unsuccessful, it’s a finger in his eye, and Trump’s; if he somehow wins, it will give Biden, or some other future Democratic president, enhanced powers to implement a left-leaning agenda. It would split the GOP wide open. The Democrats can’t lose.