Subject Matter Jurisdiction: Federal Question, Diversity, Supplemental, Removal

Federal Question Jurisdiction and the Well-Pleaded Complaint Rule

Subject matter jurisdiction (SMJ) is the court's power to hear the type of dispute. Unlike personal jurisdiction, it can never be waived, can be raised at any time (even on appeal), and the court must dismiss sua sponte if it is lacking. Federal courts are courts of limited jurisdiction: a plaintiff must affirmatively establish a basis for federal power.

Federal question jurisdiction under 28 U.S.C. 1331 exists when the claim arises under the Constitution, laws, or treaties of the United States. The key doctrine is the well-pleaded complaint rule (Louisville & Nashville R.R. v. Mottley): the federal issue must appear in the plaintiff's own properly pleaded claim, not in a defense the defendant is expected to raise, and not in an anticipated federal counterclaim.

• Trap: A plaintiff who pleads a state-law breach of contract claim and merely anticipates that the defendant will raise a federal preemption defense has NOT invoked 1331. The federal element must be part of the plaintiff's affirmative case.
• A small category of state-law claims still 'arise under' federal law where they necessarily raise a substantial, disputed federal issue that a federal forum can resolve without disrupting the federal-state balance (Grable & Sons).

Diversity Jurisdiction: Complete Diversity and the $75,000 Amount

Diversity jurisdiction under 28 U.S.C. 1332 has two independent requirements:

1. Complete diversity (Strawbridge v. Curtiss): NO plaintiff may be a citizen of the same state as ANY defendant. Diversity is measured at the time the complaint is filed.
2. Amount in controversy exceeding $75,000, exclusive of interest and costs. The plaintiff's good-faith allegation controls unless it appears to a legal certainty that the claim is for less.

Determining Citizenship

Aggregation rules

• A single plaintiff may aggregate ALL claims against a single defendant to exceed $75,000, even unrelated ones.
• Multiple plaintiffs generally may NOT aggregate separate claims, and one plaintiff may not aggregate claims against multiple defendants — unless the claim is joint (common undivided interest).

Supplemental Jurisdiction and Removal

Supplemental jurisdiction under 28 U.S.C. 1367 lets a federal court hear additional claims that lack an independent jurisdictional basis if they share a common nucleus of operative fact with an anchor claim (codifying United Mine Workers v. Gibbs) — i.e., they form part of the same case or controversy.

• The 1367(b) limit (diversity only): When the anchor is diversity jurisdiction, plaintiffs may NOT use supplemental jurisdiction over claims by/against parties joined under Rules 14, 19, 20, or 24 if doing so would destroy complete diversity. This preserves the complete-diversity requirement. (It does not bar defendants' claims.)
• A court may decline supplemental jurisdiction if the state claim raises novel/complex state issues, predominates, or all anchor claims are dismissed early.

Removal (28 U.S.C. 1441, 1446)

A defendant may remove a case the plaintiff filed in state court if a federal court would have had original jurisdiction.

• Deadline: within 30 days of receiving the first paper showing the case is removable; ALL defendants must consent.
• Forum-defendant rule: a case removable only on diversity may NOT be removed if any properly joined and served defendant is a citizen of the forum state.
• One-year cap: diversity cases may not be removed more than 1 year after commencement (absent bad-faith concealment).
• Remand for lack of SMJ is available at any time; procedural-defect remand must be sought within 30 days.

California distinction

California superior courts are courts of general jurisdiction — there is no amount-in-controversy minimum for the court's power (the $25,000 figure only sorts cases into limited vs. unlimited civil case tracks, not jurisdiction). California courts freely hear federal claims under concurrent jurisdiction unless Congress made the federal claim exclusively federal (e.g., patent, federal securities Exchange Act, bankruptcy).

Worked diversity hypothetical and timing trap

A Texas plaintiff sues a Texas defendant and an Oklahoma defendant on a $200,000 claim. Diversity fails at the outset because the plaintiff and one defendant share Texas citizenship — complete diversity is destroyed. Now suppose the Texas defendant is dismissed before trial: diversity is measured at filing, so post-filing dismissal of the non-diverse party can sometimes cure the defect, but adding a non-diverse party later destroys it. MBE trap: changing one's domicile after the complaint is filed does not create or destroy diversity — only citizenship at the moment of filing counts.

A second trap: the amount in controversy is judged from the plaintiff's perspective and good-faith pleading; a counterclaim generally cannot be used to manufacture the jurisdictional amount in the plaintiff's favor.