thumb|right|A warrant canary, posted in a Craftsbury, Vermont library in 2005: "The FBI has not been here (watch very closely for removal of this sign)". Announcing the receipt of a national security letter would violate the associated gag order, while removing the sign would not. Another provision of the USA PATRIOT Act has caused a great deal of consternation among librarians. Section 215 allows the FBI to apply for an order to produce materials that assist in an investigation undertaken to protect against international terrorism or clandestine intelligence activities. Among the "tangible things" that could be targeted, it includes "books, records, papers, documents, and other items".
tHUmB|righT|a warrant CAnarY, posTed In a craftsbuRy, Vermont libRAry iN 2005: "The fBi Has not beeN Here (wATch verY closely For rEmovAl of This siGn)". aNNOunCINg The reCeipT of a nAtioNal sEcurity letteR wOuld violate the assOcIated GAg OrdEr, wHIlE REmoviNg the sign wOuld not. anotheR provision oF the usa pAtriot aCt hAs cAUseD a great DEAl OF cOnSternAtion amonG liBrArians. SecTIon 215 allowS thE fBi To apPly foR an orDer To prodUce MatEriALs thAt AsSisT iN AN inVeSTiGAtION undeRTaKeN to pRotEct agaInsT InTernatIonal tERrorism Or clANDeStine intelligence actiVITieS. aMoNG tHe "taNgible thIngs" tHat cOUld be targeted, it InclUdes "BoOkS, rEcOrds, papers, DOcUmenTS, and othER items".