Prisoners aren’t typically allowed unfettered access to the internet, but rarely have the courts ruled on printed-out webpages. However, prisoners are often allowed copious amounts of paper, including legal briefs, books, and writing paper. In this particular case, Mark Nixon was receiving his printouts through the US Mail. The judges note that “inmates’ right to receive and send mail can be restricted for legitimate penological interests.”
Basically, Nixon is going to have to wait until he’s released to get his News Feed fix. But according to a Prisoner Assistant page, that shouldn’t be long, and in the meantime, he can receive email at his–surprise–Gmail address.