The unity of the European patent in opposition proceedings will be affected if the previous patent proprietor and the person replacing them pursuant to Art. 99(4) in respect of a particular contracting state are not deemed to be joint patent proprietors (see D‑I, 6). In this event, the opposition proceedings involving the different patent proprietors must be conducted separately. Since different requests may be submitted by the two patent proprietors (e.g. as regards amendments to the claims), the two sets of opposition proceedings may lead to different conclusions, e.g. as regards the text of the European patent or the scope of protection.
Source: http://www.epo.org/law-practice/legal-texts/html/guidelines/e/d_vii_3_2.htm
Date retrieved: 17 May 2021