The U.S. Supreme Court said Monday that it will decide whether plaintiffs can tweak their lawsuits to get them sent back to state court after a defendant has successfully gotten them placed before a federal judge.

The high court took up an appeal from Royal Canin and Purina, which are seeking to remain in federal court as they defend against a class action lawsuit over their prescription pet foods. The plaintiffs allege the foods contain no medicine and that the company says otherwise just to charge higher prices.