This dual system follows the broader constitutional division of authority. State courts predate the Constitution and retain broad power over state law. Federal courts possess limited jurisdiction over categories tied to federal law, interstate disputes, and other Article III subjects. The systems are not divided into "minor" and "important" cases. A state supreme court can decide a major constitutional issue, and a federal district court can decide a relatively narrow statutory claim.

Concurrent jurisdiction means that more than one system is legally available at the start. It does not allow a losing party to conduct the same case twice. Rules governing removal, preclusion, and appellate review coordinate the systems. Removal moves a qualifying case into the federal trial system; it is not an appeal from the state judge's merits decision.

State courts must apply controlling federal law when it governs a case. The Supremacy Clause does not turn them into lower federal courts; they remain state institutions. Their judgments on federal issues may ultimately be reviewed by the U.S. Supreme Court, while their final interpretations of state law ordinarily remain beyond federal correction.

Federal courts also apply state substantive law in some cases, especially diversity litigation, rather than creating a general federal common law for ordinary state disputes. That interaction prevents a party from obtaining a completely different body of state law merely by entering federal court. The federal forum and the governing law are separate questions.

The systems also interact through precedent and remedies. A federal court deciding state-law issues generally respects authoritative state interpretations. A state court deciding a federal constitutional issue must follow controlling Supreme Court precedent. "Dual court system" therefore means institutional overlap with different sources of authority, not two legal worlds that never meet.

A common distractor claims that every federal constitutional issue must begin in federal district court. State judges routinely decide federal questions. The decisive facts are jurisdiction and appellate route, not the word "federal" in the claim.

Retrieval check. For any case, identify the source of the claim, the basis of jurisdiction, the court of original filing, and the lawful appellate route.

Video lesson: Structure of the Court System: Crash Course Government and Politics #19