Federal question jurisdiction refers to the power granted to U.S. federal courts to hear cases involving matters pertaining to the U.S. Constitution or other federal laws. This type of jurisdiction falls under the category of subject-matter jurisdiction, meaning that the court that hears the case is determined by the subject matter involved. The basis for this power comes from Article III of the U.S. Constitution. A federal court may override the jurisdiction of a state court if a federal question is at hand, which means the cause of action in the case arises under federal law.
Along with diversity jurisdiction, which involves parties from different states, federal question jurisdiction is one of the two main types of subject-matter jurisdiction. Article III of the U.S. Constitution stipulated for this jurisdiction, but only on the condition that the U.S. Congress pass a statute to that effect. After various judiciary acts passed by Congress left federal courts in limbo as to which cases they could hear, an act passed in 1875 finally gave the power to all lower federal courts to hear civil cases with a federal question.
A federal question arises when a plaintiff in a civil case claims that he or she has been wronged by an action that violates either a federal law, the Constitution, or a treaty involving the U.S. When this occurs, federal question jurisdiction can take place, overriding the jurisdiction of the state or states of the cause of action or the parties involved. For example, a worker and a boss who get into a dispute over the worker's firing would normally be a case for a state court. If the worker feels he or she was fired due to some discrimination, then that would be a Constitutional issue and therefore subject to federal question jurisdiction.
Any plaintiff claiming a federal question must have the question involved spelled out in the complaint. Federal question jurisdiction cannot be claimed simply if the plaintiff anticipates that the opposing party will use a federal law or the Constitution as a basis for defense of the case. There need be no amount of controversy involved for this type of jurisdiction to take place. In other words, a federal court can hear such a case even if no money is at stake, which is not the case with diversity jurisdiction.
The U.S. Supreme Court acts as the ultimate arbiter about what cases fall under federal question jurisdiction. Past rulings have left what constitutes a federal question up for debate. They have ruled that state law cases can be brought into a federal court even if only tangentially connected to a federal issue. In other cases, they have ruled that only substantial federal issues must be at hand for a case to be considered a federal question.