The Constitution does not require Congress to create lower federal courts. The Framers assumed that state courts would be competent to hear the cases included in Article III's definition of the judicial power of the united states. When Congress does choose to confer some of the federal judicial power on lower federal courts, state courts normally retain their jurisdiction as well. This simultaneous or concurrent jurisdiction of state and federal courts normally exists unless Congress enacts a law stating that the federal power shall be exclusive. Only in unusual circumstances, as when state jurisdiction would gravely disrupt a federal program, has the Supreme Court required an explicit grant of congressional authority for concurrent state jurisdiction to exist. Indeed, in the limited instance of diversity jurisdiction, the Framers intended concurrent jurisdiction to be mandatory, so that Congress could not divest state courts of judicial power they possessed before adoption of the Constitution.
Concurrent jurisdiction allows plaintiffs initial choice of a forum more sympathetic to their claims. In many circumstances, however, a defendant may supplant that choice by exercising a right under federal law to remove the case from state to federal court. (See removal of cases.)
State courts need not always agree to exercise their concurrent jurisdiction. If a state court declines to hear a federal claim for nondiscriminatory reasons tied to the sound management of the state judicial system, the Supreme Court will respect that decision.
When concurrent jurisdiction exists, state and federal courts may be asked to adjudicate the same rights or claims between parties at the same time. Ordinarily neither the federal nor the state court is required to stay its proceeding in such situations. However, the federal courts do possess a limited statutory power to enjoin pending state proceedings, and a state or federal court that is the first to obtain custody of property that is the subject of the dispute may enjoin the other.
Carole E. Goldberg -Ambrose
Currie, David 1981 Federal Jurisdiction in a Nutshell, 2nd ed. St. Paul, Minn.: West Publishing Co.