The hurlyburly's done, and the Enlarged Board of Appeal (EBA) of the European Patent Office (EPO) has now issued its decision in case G 4/19 regarding "double patenting", i.e. the circumstances, if any, in which a patent proprietor might be granted two patents for the same subject matter. Essentially, the EBA confirmed that double-patenting is prohibited, in all circumstances, at the EPO, and that the prohibition has legal basis in the European Patent Convention (EPC).

"Double patenting" arises where identical subject-matter is pursued by the same applicant in two or more European patent applications which have the same effective filing date and designate the same state(s). Double-patenting most commonly occurs in the case of overlapping parent and divisional applications (for example, the not uncommon situation where to maximise the disclosure of the application as filed, a divisional application is filed identical to the parent application as filed), and in cases of "internal priority", i.e. where a second European patent application claims priority from a first.

It is the long established practice of the EPO Examining Division to refuse patent applications for double-patenting, despite there being no explicit prohibition in the EPC. EBA decisions G 1/05 and G 1/06 confirmed that an applicant has "no legitimate interest" in the grant of a second patent to the same subject‑matter, and the EPO Guidelines for Examination (G-IV, 5.4) give Article 97(2) in conjunction with Article 125 EPC as the legal basis for refusal of a patent application on these grounds. The Guidelines state that to avoid double-patenting one or more of the applications must either be amended so the claims of the applications are not identical, overlapping designations must be withdrawn, or the applicant must choose one of the applications to proceed to grant. If none of these actions is taken then once one of the applications is granted the other(s) will be refused.

In the case in point, European patent application number 10718590.2 (Société des Produits Nestlé S.A.) was refused by the Examining Division for double-patenting, on the basis that claim 1 of the sole claim request on file was directed to subject-matter which was identical to the subject-matter claimed in European patent number 2251021, which was granted for the European patent application from which the application-in-suit claimed priority (i.e. double patenting through "internal priority"). 

In its appeal against this decision to refuse the application (T 318/14), the applicant argued that the prohibition against double-patenting did not apply in a situation of "internal priority": decisions G 1/05 and G 1/06 related to divisional applications, not internal priority, and there was a "legitimate interest" in the grant of a second patent, since the second patent would have a longer term of protection than the first patent as a result of claiming internal priority (a patent term runs for up to 20 years from the filing date, not the priority date).

In reaching its decision, the EBA found that Article 125 EPC can provide a legal basis for the regulation of double-patenting. Whilst Article 125 EPC refers "the principles of procedural law generally recognised in the Contracting States", and is one of the EPC "Common Provisions Governing Procedure", there was nothing to suggest that it could not apply to "substantive" issues: for example, Article 123 EPC [regarding amendments, the European patent attorney's favourite Article] is also within this section of the EPC and clearly relates to "substantive" issues, some of which are grounds of revocation of a patent.

A detailed examination of the preparatory documents for the drafting of the EPC (back in the early 1970s), led the EBA to conclude that a prohibition on double-patenting was a "principle generally recognised in the contracting states", and thus fell under Article 125 EPC. The EBA found that the preparatory documents clearly showed that the prohibition should apply to patents and applications having the same "effective date" (i.e. priority date), and that no special circumstances or conditions need to apply, i.e. all cases are covered.