Post-class discussion suggested some confusion on something, so let me offer some clarification here:
We said two things in class:
1) Under § 1367(a), a court can exercise supplemental jurisdiction only if it had original jurisdiction. So if the anchor claim is dismissed for lack of subject matter jurisdiction, the court never had supplemental jurisdiction.
2) Under § 1367(c)(3), the court may decline supplemental jurisdiction if the anchor claim has been dismissed. But the court may elect to keep supplemental jurisdiction, even if the anchor claim is gone.
How do we reconcile? The key is identifying when a dismissal is a 12(b)(1) or a 12(b)(6)--If 12(b)(1), then supplemental jurisdiction is gone; if 12(b)(6), then the court could keep the supplemental claims. SCOTUS over the past decade has decided several cases identifying when a dismissal is (b)(1) or (b)(6), noting every time that the effect of supplemental jurisdiction is one of the key consequences of identifying the dismissal as one or the other.
One thing to recognize, however, is the general rule that the dismissal of a claim on the merits does not retroactively deprive the court of jurisdiction. Jurisdiction is established by the allegations in the well-pleaded complaint and the failure of those claims on the merits does not change that. So, for example, that the copyright claims in Naruto are dismissed for failure to state a claim because a macaque has no rights under the Copyright Act does not mean the court lacked jurisdiction. Similarly, if the 14th Amendment claims in Godin are dismissed, there was jurisdiction because federal law created Godin's cause of action and provides the rule of decision; this means the court can exercise and retain (if it chooses) supplemental jurisdiction over the state claims.