A class action alleges GM has falsely claimed its ACDelco auto parts are made in the United States as a way to induce customers into paying a premium price for items they believe to be American-made.
www.classaction.org
A class action lawsuit alleges the ACDelco "Made in USA" claim is false, inducing consumers to purchase auto parts marketed and sold by General Motors but made in China.
www.carcomplaints.com
On a class action suit, the attorney probably took this case for a percentage of damages; meaning it's a case where the attorney is sure enough of himself/herself to spend time on it without being paid until settlement.
IF I WERE THE ATTORNEY, which I'm not, I would think they would have the common sense to go buy several more of these filters as "demonstration;" leaving some of them sealed in original packaging and opening at least one or two to personally substantiate the observation of packaging stating "made in USA" vs product in packaging stamped "made in China." I'd buy a dozen or more with the specific purpose in mind of letting members of the jury open them in court. And I would do all the aforementioned prior to filing class action suit.
And I'm no attorney and I am ignorant of many legal things, but I think you must have a minimum of 3 plaintiffs for "class action."