Jacqui Cheung has the details at Ars Technica. It is worth noting that the dissenting judges in the opinion were strongly opposed to the majority of judges who overruled them, making network censorship legal in libraries, at least in the state of Washington. The case was heard by the state’s supreme court on appeal and is a straight forward challenge of a policy of filtering known pornography, gambling sites, web chat and proxy avoidance services with little or no exception.
I think the reasoning given by the judges pushing the ruling is hugely flawed. They compare internet access to the stacks claiming the library is not obligated to put out materials that are protected speech, like pornography magazines. There is a torturous implication about managing limited space and resources. Access to the internet is limited in some regards, by each libraries fixed number of terminals and bandwidth but not the content reachable through them. If disproportionate usage of the limited parts is a concern, censorship is not the answer, rules and software to limit the duration of access would make far more sense. Problematic sites require active searching and browsing and any accidental exposure is no doubt easily handled by an idle reset in the software used.
I have no problem with trying to ensure that libraries remain family friendly environments or trying to deal with the problems posed by certain kinds of online exploitation but censorship is never going to be an appropriate solution. Comparing the internet to stacks isn’t going to change that, the two just do not work at all in the same fashion. Any ruling on genuine problems presented by offering public access in a public facility needs to be based on the reality of how such network access works, not on a deeply flaw analogy to other resources that happen to fall under the same purview of the library staff.