The validity of another Oracle patent has become doubtful in the dispute with Google about the infringement of Java patents and copyrights on Android devices. The US Patent Office and Trademark Office (USPTO) has provisionally declared all 24 claims of patent number 6,125,447 as being invalid. The USPTO based its decision on a patent that had been used in another case. This patent was granted in 1994 – three years before Sun filed its Java patent application. The US patent office also considered two publications released in 1996 as evidence that Sun's described method for protecting applications via "protection domains" was anticipated by "prior art."Emphasis mine.
This is a related item to patent 6,192,476 which covers a broad method "for determining whether a principal (e.g. a thread) may access a particular resource."
Patent 6,125,447 describes "maintaining and enforcing security rules using protection domains."