Network connections are usually rented from service providers . The service providers control the access their clients receive. This is another approach to the pornography problem, whereby some service providers have agreed to attempt to not allow certain kinds of material to be accessed via their facilities. One problem with any attempt to screen material is the sheer size of the network. New material is added hourly and most screening relies on human intervention.
Technology can help.
For instance, SurfWatch is a piece of software that blocks access to specific sites. Nevertheless the database that the software uses to identify those sites must be maintained with human assistance. The geographical diversity causes further problems. Such questions of jurisdiction do not apply only to accessibility legislation but the answers are not clear-cut. It depends on the exact basis of the legal challenge.