The phrase "questionable validity" means that something is doubtful or uncertain in terms of its truth or accuracy. It suggests that there are doubts about the reliability or credibility of whatever is being discussed. Full definition
In addition, many companies, especially small businesses, preferred to license patents of questionable validity rather than risk litigation. (eff.org)
To understand, think about the patent troll business model: making broad claims of infringement based on patents of questionable validity is the troll's favorite move. (eff.org)
For some classic stories of questionable validity put to film, look for Tall Tale starring Patrick Swayze. (parentpreviews.com)