Article III, Section 2, Clause 2: Jurisdiction

In all Cases affecting Ambassadors, other public Ministers and Consuls, and those in which a State shall be Party, the supreme Court shall have original Jurisdiction. In all the other Cases before mentioned, the supreme Court shall have appellate Jurisdiction, both as to Law and Fact, with such Exceptions, and under such Regulations as the Congress shall make.

This clause addresses the jurisdiction of federal courts. When a court is established, its jursidiction (which cases it is authorized to hear and rule on) must also be defined. Jurisdiction is also split into original and appellate jurisdiction. A case must first be brought before a court having original jurisdiction to hear the case. The decision of this court may subsequently be appealed to a court having appellate jurisdiction if one of the parties to the case is unhappy with the original decision and claims legal grounds to question it.

The Supreme Court is granted original jurisdiction over cases affecting diplomats or in which a state is one of the parties to the case. SCOTUS has ruled that this grant of jurisdiction in the Constitution is not subject to being either expanded or contracted by Congress and required no enabling legislation by Congress. Concerns over infringement of state sovereignty were subsequently addressed by the 11th Amendment. However, original jurisdiction in all other cases belongs to inferior courts; furthermore, Congress has  broad powers to define the jurisdiction of these courts. This means that Congress can, in principle, remove jurisdiction over certain cases from the federal judiciary completely, by failing to enact enabling legislation granting that jurisdiction to any inferior court.

This power is not absolute. SCOTUS has overruled attempts by Congress to vitiate constitutional rights by limiting the jurisdiction of the courts. Thus case brought to enforce constitutional rights cannot be voided by any Congressional manipulation of jurisdiction.