LAW 521-002 – Civil Procedure I
Federal Question Jurisdiction
The district courts shall have original jurisdiction of all civil actions arising under the Constitution, laws, or treaties of the United States.
"Arising under" means the claim is “substantially founded” on a federal law.
The well-pleaded complaint rule says that the federal question must be part of plaintiff's complaint. It cannot be a defense of the defendant's that is merely anticipated. Louisville & Nashville Railroad Co. v. Mottley.