The European Patent Convention contains no explicit provision dealing with double patenting. However, the Guidelines state that "it is an accepted principle of most patent systems that two patents shall not be granted to the same applicant for one invention" and go on to state that where the examiner is aware of two applications having the same dates and the same claims, "the applicant should be told that he must either amend one or more of the applications in such a manner that they no longer claim the same invention, or choose which of the applications he wishes to proceed to grant". The examining division applied these guidelines in Divisional claim conflicting with parent/Komag Inc. In this case, the parent application had proceeded to grant claiming a combination of features A and B. The examining division rejected a divisional application claiming feature A on the ground that, since the claim did not exclude the possibility of B being present, the claim of the divisional was reclaiming that which had been claimed in the parent.

The Board of Appeal disagreed. It found that it did not have to decide the general question of whether there was a prohibition on double patenting in European patent law because in the present case, the claims were of different scope and so not directed to the same invention. The Board specifically found that: