In order to avoid the Common European Asylum System becoming non-functional due to mass arrivals of such extraordinary scale and intensity that, even if a Member State has a well-prepared asylum, reception and return system, if the situation is not addressed by the Union as a whole, it could create a serious risk of serious deficiencies in the treatment of applicants, the Member State should, in those most exceptional circumstances, be able to be relieved of its obligation to take back an applicant pursuant to Article 16(2) and Article 38(4) of . However, in order to ensure that the application of such a derogation does not lead to additional pressure on the Member State facing that situation, that derogation should only apply retroactively to applications already registered in that Member State within four months before the date on which the Council implementing decision is adopted.