As from the time when a third party proves to the EPO that they have initiated proceedings concerning entitlement (see A‑IV, 2.2) and up to the date on which the EPO resumes the proceedings for grant (see A‑IV, 2.2.5), neither the European patent application nor the designation of any contracting state may be withdrawn.[Rule 15; ]
Source: http://www.epo.org/law-practice/legal-texts/html/guidelines/e/a_iv_2_3.htm
Date retrieved: 17 May 2021