The object and purpose of the exclusion under Art. 53(b) EPC was not, however, sufficiently obvious to answer the question whether or not the clause was to be construed in a narrow or broad way. The Enlarged Board noted that under Art. 31(3) of the Vienna Convention any subsequent agreement between the parties regarding the interpretation of the treaty or its application, and any subsequent practice in the application of the treaty which establishes the agreement of the parties regarding its interpretation is to be taken into account. It pointed out that R. 26(5) EPC (formerly R. 23b(5) EPC 1973) could be regarded as such subsequent agreement and practice. R. 26(1) EPC explicitly calls for due consideration of the Biotech Directive (see G 2/06, point 16 of the Reasons).

The interpretation of the Biotech Directive as put forward in the Commission Notice (2016) could not be seen as a relevant development because it has not been confirmed in a legally binding way. If the adoption in 2017 of R. 28(2) EPC – in accordance with the interpretation developed in the Notice – by the Administrative Council were to be considered a subsequent agreement in the sense of the Vienna Convention and used for the interpretation of Art. 53(b) EPC, this would reverse the meaning of Art. 53(b) EPC as interpreted by the EBA in decisions G 2/12 and G 2/13, i.e. it would represent an amendment of an Article of the Convention. However, the Administrative Council is not, in the light of Art. 33(1)(b) and 35(3) EPC, competent to amend the Convention, here Art. 53(b) EPC, by amendment of the Implementing Regulations, here R. 28(2) EPC. The decision to adopt R. 28(2) EPC could not be regarded as a subsequent agreement between the parties that shall be taken into account for the interpretation of the treaty, in the meaning of Art. 31(3)(a) of the Vienna Convention (T 1063/18). See also the pending referral under G 3/19.