3. The principal case was overruled on other grounds by California Dept. of Water Resources v. Powerex Corp., 533 F.3d 1087 (9th Cir. 2008), holding that a district court’s discretionary decision to decline supplemental jurisdiction may be challenged by appeal, rather than a petition for writ of mandamus. Review by mandamus is far more difficult to obtain than appellate review, which is discussed at length in Chapter 16.