A US Inventor has recently been given permission by the US court system to challenge the validity of two patents which he was a named inventor on.

Under the US system, inventors are also Applicants on filing. As such, Mr. Cheriton would have originally been an assignor and prevented from challenging the patents under assignor estoppel.

Mr. Cheriton had set up a new company, which presumably wanted to act within the scope of these patents.

The European Patent Office prevents self-opposition, but there is nothing preventing inventors from opposing patents they are named on. Perhaps worth considering if internally there are doubts about a patent's validity!