West's Encyclopedia of American Law | Abstention Doctrine

The concept under which a federal court exercises its discretion and equitable powers and declines to decide a legal action over which it has jurisdiction pursuant to the Constitution and statutes where the state judiciary is capable of rendering a definitive ruling in the matter.

The abstention doctrine was adopted by the Supreme Court to allow the federal judiciary to refrain from ruling on constitutional questions. Because it has no explicit source in federal or state laws, it is the exception to the general rule that a litigant may sue or be sued in federal court if the federal court has jurisdiction, or power to hear the case. A federal court has jurisdiction over several species of cases and controversies, such as those involving a federal constitutional question, a federal statute, or litigants of different states in a dispute totaling over $50,000 (in which case, the court's power to hear is called diversity jurisdiction)....