Black-letter propositions
- 01
Claims share a constitutional case when they derive from a common nucleus of operative fact.
- 02
In diversity-only cases, section 1367(b) restricts specified claims by plaintiffs against parties joined under Rules 14, 19, 20, or 24 and claims by certain proposed plaintiffs.
- 03
The court may decline when the state claim is novel or complex, substantially predominates, all federal claims are dismissed, or exceptional circumstances provide compelling reasons.
- 04
A qualifying claim may enter even if it does not independently satisfy the amount in controversy.
Use this attack sequence under time
Frame the issue
Find an original jurisdiction anchor.
Resolve the next checkpoint
Test common nucleus.
Resolve the next checkpoint
If diversity is the sole anchor, apply the plaintiff-side statutory exclusions.
Finish the conclusion
Consider discretionary decline only after power exists.
Common wrong turns
- Supplemental jurisdiction never creates original jurisdiction from nothing.
- Do not apply the diversity limitation to federal-question cases or to ordinary defendant claims without checking its text.
Worked example
A diverse plaintiff brings a $100,000 claim against one defendant and a related $20,000 claim against a second diverse defendant joined under Rule 20.
If complete diversity remains, the smaller related claim may fall within the same case, but a plaintiff's Rule 20 claim in a diversity-only action is within the statutory limitation; determine whether it independently meets diversity requirements.
Practice this topic
Section 1367's structure
28 U.S.C. 1367(a) gives district courts supplemental jurisdiction over all other claims that are so related to claims within original jurisdiction that they form part of the same case or controversy under Article III. It includes claims involving joinder or intervention of additional parties.
Subsection (b) limits that grant in cases founded solely on diversity. The district courts do not have supplemental jurisdiction over claims by plaintiffs against persons made parties under Rule 14, 19, 20 or 24, or over claims by persons proposed to be joined as plaintiffs under Rule 19 or seeking to intervene as plaintiffs under Rule 24, when exercising it would be inconsistent with the requirements of section 1332.
Discretion to decline, and tolling
Subsection (c) lets a court decline supplemental jurisdiction if the claim raises a novel or complex issue of State law, substantially predominates over the claims within original jurisdiction, all original-jurisdiction claims have been dismissed, or in exceptional circumstances there are other compelling reasons. Subsection (d) tolls the limitations period for a claim under (a) while it is pending and for 30 days after dismissal unless State law provides a longer period.
Because subsection (b) targets plaintiffs' claims against persons joined under specific rules, a defendant's compulsory counterclaim or third-party claim is analyzed under (a) instead.
Frequently asked questions
What is the controlling rule for supplemental jurisdiction?+
Supplemental jurisdiction covers claims within the same Article III case, but diversity-only plaintiff claims listed in section 1367(b) remain restricted.
What is the same case or controversy standard?+
28 U.S.C. 1367(a) grants supplemental jurisdiction over claims so related to original-jurisdiction claims that they form part of the same case or controversy under Article III.
Does supplemental jurisdiction include additional parties?+
Yes. Section 1367(a) says it includes claims that involve the joinder or intervention of additional parties.
What limits apply in diversity cases?+
Under section 1367(b), no supplemental jurisdiction over plaintiffs' claims against persons joined under Rules 14, 19, 20 or 24 when that would be inconsistent with section 1332.
When may a court decline supplemental jurisdiction?+
If the claim raises a novel or complex issue of State law, substantially predominates, all original claims were dismissed, or other compelling reasons exist in exceptional circumstances.
What does section 1367(d) do to limitations periods?+
It tolls the limitations period for a claim while it is pending and for 30 days after dismissal, unless State law provides a longer tolling period.