government's interest in preventing the dissemination of such
speech cannot justify the use of the technology protection
measures mandated by CIPA, which necessarily block substantial
amounts of constitutionally protected speech.


CIPA thus resembles the Communications Decency Act, which
the Supreme Court facially invalidated in Reno v. ACLU, 521 U.S.
844 (1997). Although on its face, the CDA simply restricted the
distribution to minors of speech that was constitutionally
unprotected with respect to minors, as a practical matter, given
Web sites' difficulties in identifying the ages of Internet
users, the CDA effectively prohibited the distribution to adults
of material that was constitutionally protected with respect to
adults. Similarly, although on its face, CIPA, like the CDA,
requires the suppression of only constitutionally unprotected
speech, it is impossible as a practical matter, given the state
of the art of filtering technology, for a public library to
comply with CIPA without also blocking significant amounts of
constitutionally protected speech. We therefore hold that a
library's use of a technology protection measure required by CIPA
is not narrowly tailored to the government's legitimate interest
in preventing the dissemination of visual depictions that are
obscene, child pornography, or in the case of minors, harmful to
minors.
For the same reason that a public library's use of software
filters is not narrowly tailored to further the library's
interest in preventing its computers from being used to
disseminate visual depictions that are obscene, child
pornography, and harmful to minors, a public library's use of