This article reviews the recent IP Australia decision in Grant's Application [2004] APO 11 about an innovation patent for a way of protecting assets against a loss of ownership as a result of a legal liability. The significance of this decision was to expose the tortured reasoning necessary to exclude from patentability an invention that was arguably contrary to the "public interest". The article asserts that the effect of the decision revoking the patent was correct, but that the reasoning points to a need to reconsider the "public interest" limits on patentability. The article then considers the approach that should be adopted in formalising a "public interest" exemption from patentability that is practical and generally applicable.