Weeks v. United States (1914) was a US Supreme Court case whose sentence established, by unanimity, that the warrantless seizure of personal objects from a private domicile is a violation of the Fourteenth Amendment. It also addresed local officers, to forbid them to collect evidence by mechanisms which are banned by the exclusionary rule, and afterwards give that evidence to their federal colleagues.
The exclusionary rule is a legal principle interpreted from the US constitution. It determines that the evidence which is collected through a mechanism that violates the defendant's consitutional rights, cannot be used in a court of law.