The Federal Circuit has declined to overturn a pair of final decisions by the Patent Trial and Appeal Board (PTAB) that cancelled claims from a VirnetX Inc. patent in an Apple inter partes review (IPR), holding that the NPE’s appeal was barred by issue preclusion. VirnetX had challenged the Board’s June 2017 decisions that certain claims from the challenged patent were invalid as obvious in light of a single prior art reference. However, in a December 10 opinion, the Federal Circuit held that VirnetX was collaterally estopped from disputing whether that reference was prior art, since in March 2017 the court had summarily affirmed multiple PTAB decisions that the same reference qualified as a printed publication in several other Apple IPRs against related patents (2017-2490, 2017-2494). Issue preclusion was applicable here in the Rule 36 context, the court ruled, because those decisions necessarily turned on a single issue: whether the aforementioned reference counted as prior art for the challenged patent family. The Federal Circuit also declined to allow VirnetX to proceed based on an alternative, constitutional argument, holding that it had failed to properly preserve the issue.