P sued to recover damages from the F.B.I. for imprisoning P in violation of their Constitutional rights and subjecting their premises to unreasonable search and seizure. D moved to dismiss for a failure to state a cause of action for which relief could be granted and for summary judgment, on the grounds that federal agents acted within the scope of their authority and that the searches and seizures were incidental to lawful arrests. The judge dismissed the suit for want of federal jurisdiction, as the action did not arise under the Constitution or the law of the United States. The Court of Appeals affirmed. The court denied P a motion to amend. The Supreme Court granted certiorari.