Double Patenting Without Evergreening: Missing The Forest For The Trees?

The judge-made law of double patenting prevents a patentee from obtaining more than one patent for the same invention, and prohibits claims in a second patent that are not patentably distinct from those of the first patent. The purpose of the rule—according to the Supreme Court—is to prevent a patentee from "evergreening" its monopoly by obtaining successive patents for the same invention, or obvious variations. However, the Federal Court of Appeal has recently¹ held that double patenting applies to divisional patents—at least those that are considered to be "voluntary" divisionals—that expire on the same date as their parent, and are therefore incapable of "evergreening" a patentee's monopoly.