An interesting recent Federal Court decision considered file wrapper estoppel during a summary judgment motion.  The Defendant successfully argued to have the Court consider the file wrapper of the corresponding US application, based on s. 53.1 of the Patent Act.  While the Court acknowledged that the statute is limited to communications between the patentee and the Canadian Patent Office, is only admissible for the limited purpose of rebutting a representation made by the patentee as to the construction of a claim in the patent, and held that generally foreign prosecution history should be inadmissible, absent “extraordinary circumstances”, the Court did look at the US application history in its purposive construction of the claims of the Canadian patent.  “Extraordinary circumstances” were found to arise because the patentee had acknowledged that the claims had been amended to substantially match those in the foreign jurisdiction and had admitted that the amendments limited the claims to make them novel and non-obvious.  The patentee had made the foreign prosecution history part of the Canadian file wrapper by doing so.