The admissibility of the opposition, being an indispensable procedural requirement for any substantive examination of the opposition submissions, must be checked ex officio in every phase, including any ensuing appeal proceedings (TÂ 240/99).
Source: http://www.epo.org/law-practice/legal-texts/html/caselaw/2019/e/clr_v_a_3_2_1_a.htm
Date retrieved: 17 May 2021