Petitioners' class action complaint brought in state court seeking relief under Missouri law for respondents' marketing of fake prescription pet food products raised neither a substantial nor a disputed federal question. In ruling nonetheless that federal courts have subject-matter jurisdiction over this suit, did the court of appeals introduce chaos into this Court's coherent jurisprudence about when federal question jurisdiction will lie over state-law claims?

Whether the court of appeals erred in finding federal question jurisdiction over a state-law class action complaint alleging marketing of fake pet food products