A more thorough explanation:

Definition: Federal question jurisdiction is a way for a federal court to have the power to hear a case. This happens when the case involves a question of federal law. There are both constitutional and statutory requirements that must be met before jurisdiction can be found.

Under the Constitution, federal courts can hear "all cases, in law and equity, arising under this Constitution, [and] the laws of the United States..." This means that if a case involves a question of federal law, a federal court can hear it. For example, if someone sues the federal government for violating their constitutional rights, a federal court can hear the case.

For federal question jurisdiction to exist, the requirements of 28 USC 1331 must also be met. This statute gives federal courts jurisdiction only to those cases which "aris[e] under" federal law. This means that the case must involve a question of federal law. For example, if someone sues a company for violating a federal law, a federal court can hear the case.

Typically, in order to have federal question jurisdiction, the plaintiff's complaint must be a well-pleaded one. This means that the plaintiff's initial complaint must contain references to the federal question and the federal issue evoked. The federal question and issue cannot arise in an anticipated defense, it must be presented from the initial complaint. For example, if someone sues a company for violating a federal law, the complaint must specifically mention the federal law that was violated.

Another test that courts will often use to determine federal question jurisdiction is called the Grable Test. This is a two-part test:

1. Does the claim have a "federal ingredient" for federal question jurisdiction under Article III Section 2 of the Constitution?
2. Does the claim meet the requirements for 28 USC 1331 federal question jurisdiction?

For example, if someone sues the IRS for improperly seizing their property, the case may involve a question of federal law. The Grable Test would be used to determine if a federal court can hear the case.