Traditionally, "double patenting" has been a non-issue in Canada. There are no statutory provisions dealing with double patenting – merely language suggesting that one patent is to be granted for one invention. At the Patent Office (CIPO) level, that has been taken to mean that different applications may contain similar claims as long as they are not the same.

However, the case GlaxoSmithKline v. Apotex case has brought "obvious-type" double patenting to the forefront with CIPO.

The case was decided in the context of Canada's special rules for pharmaceutical inventions and is more than a little curious. The Judge's comments on double patenting may be considered as merely obiter. Nevertheless, the case is being cited by CIPO Examiners as requiring that claims in a divisional application must be non-obvious over claims in a parent application. Some Examiners have even extended that reasoning to co-pending applications where one is not a divisional of the other.

It seems illogical to permit Examiners to reject co-pending claims as obvious over one another when they are in commonly owned applications, but not when they are in applications that are owned by different parties. Further, there is no basis for the practice in the Patent Act or Rules and no guidelines as to how obviousness is to be judged on a claim versus claim basis. The traditional view has been that double patenting is a "sin" only if granted patents are misused. In other words, it is a question of how the patents are used after they have been granted – not whether they should be granted in the first place.

Quite where this is leading is not clear. Examiners seem reluctant to issue "final" office actions – which would allow applicants to proceed before the Patent Appeal Board. As such, it remains to be seen whether or not the Board will take the view that Examiners should go back to the "co-terminous" test and leave it to the Courts to decide on the "sins" of the patentee.