Bivens v. Six Unknown Named Agents was a case in which federal agents searched a man’s house without a warrant, establishing that a person may sue the federal government if his rights are violated.
Agents of the Federal Bureau of Narcotics searched Bivens’s house without a warrant. Bivens sued the federal government in 1971 for violating his Fourth Amendment right against unlawful search and seizure.
The court determined that Bivens was entitled to damages from the federal government.
"…[Federal] courts do have the power to award damages for violation of 'constitutionally protected interests' and I agree with the Court that a traditional judicial remedy such as damages is appropriate to the vindication of the personal interests protected by the Fourth Amendment." (Wikipedia)
The District Court had dismissed the case saying that Bivens had no grounds for damages, but the Supreme Court reversed the decision, determining that you could sue the federal government for damges.