Federal Question Jurisdiction.

 Federal question jurisdiction refers to the authority of federal courts in the United States to hear and decide cases involving issues of federal law. This jurisdiction is based on the provisions of the United States Constitution and federal statutes.

Under Article III, Section 2 of the U.S. Constitution, federal courts have jurisdiction over cases "arising under the Constitution, laws, or treaties of the United States." This means that federal courts can hear cases that involve the interpretation, application, or enforcement of federal law. Examples of federal law include constitutional provisions, federal statutes, regulations issued by federal agencies, and treaties ratified by the United States.

Federal question jurisdiction is one of the two primary bases for federal court jurisdiction, along with diversity jurisdiction. Diversity jurisdiction allows federal courts to hear cases between citizens of different states when the amount in controversy exceeds a certain threshold. Federal question jurisdiction, on the other hand, does not depend on the parties' citizenship but rather on the presence of a federal question or issue of federal law in the case.

To establish federal question jurisdiction, the federal question or issue of federal law must be a substantial part of the plaintiff's claim or the defendant's defense. If the case involves both federal and state law claims, federal courts have jurisdiction over the entire case, including the state law claims, through a doctrine known as "supplemental jurisdiction" or "pendant jurisdiction."

The Supreme Court of the United States is the highest court in the federal judiciary and has ultimate authority to interpret federal law. However, federal question cases can also be heard in lower federal courts, such as the U.S. district courts and the U.S. courts of appeals.

It's important to note that federal question jurisdiction is not automatic. The plaintiff must raise a federal question in the complaint or the defendant can assert a federal defense. The court will then evaluate whether the federal question is substantial and whether it has jurisdiction to hear the case based on the federal question jurisdiction.