Law
Qualified Immunity in Constitutional Tort Claims
Quick fact
Qualified immunity was created by the Supreme Court in 1967 (Pierson v. Ray), not by Congress, and it protects officials unless the violated right was 'clearly established' to the same degree that a reasonable official would know their conduct was unlawful.
Why this is interesting
A police officer can kick down your door without a warrant, and if you sue, an officer who violates your constitutional rights may never face a judgement—all because of a legal shield you've never heard of.