In litigation about Windex products that were advertised as non-toxic, a group of class-action plaintiffs sued S.C. Johnson & Son in federal court in Wisconsin and opted out of a subsequently-filed state-court class action in California. And back in Milwaukee, they pursued a collateral attack on a settlement in the California case as being the product of a reverse auction that deprived the absent class members of due process.Because the Wisconsin plaintiffs sued first, it wasn’t clear whether the state-court settlement …