In G 2/02 and G 3/02 (OJ 2004, 483) the Enlarged Board of Appeal recognised that, in accordance with the aim of the EPC, as expressed in its preamble, to strengthen co-operation between the States of Europe in respect of the protection of inventions, there has always been the intention to harmonise the substantive patent law to be applied in the Contracting States and in the EPO.

In G 5/83 the Enlarged Board of Appeal stated that in the interpretation of international treaties which provide the legal basis for the rights and duties of individuals and corporate bodies it is, of course, necessary to pay attention to questions of harmonisation of national and international rules of law. This aspect of interpretation, not dealt with by the provisions of the Vienna Convention, is particularly important where, as is the case with European patent law, provisions of an international treaty have been taken over into national legislation. The establishment of harmonised patent legislation in the Contracting States must necessarily be accompanied by harmonised interpretation. For this reason, it is incumbent upon the European Patent Office, and particularly its boards of appeal, to take into consideration the decisions and expressions of opinion of courts and industrial property offices in the Contracting States. In T 154/04 (OJ 2008, 46) the board stated that in the proceedings before the European Patent Office, such considerations do not exonerate a board of appeal from its duty as an independent judicial body to interpret and apply the EPC and to decide in the last instance in patent granting matters. In addition, despite harmonised legal regulations it is not self-evident that their interpretation is also harmonised among different national courts, let alone courts of different contracting states, so that the boards of appeal would be at a loss as to which interpretation to follow if they did not exercise their own independent judgment.