The Code of Belgian Nationality allows the application for nationality provided that one has had a "legal residence" for a certain period of time, depending on the case. For a child, it is sometimes the parents who must be able to prove a legal residence.
When the Code of Belgian Nationality was last amended by a law of December 4, 2012, a royal decree of January 14, 2013 clarified how proof of legal residence could be provided. However, it soon became evident that the list drawn up was incomplete. Indeed, the failure to take into account certain types of residence for European citizens or their family members directly contradicted the rules established by Directive 2004/38 of the European Parliament and Council on the right of citizens of the Union and their family members to move and reside freely within the territory of the Member States regarding free movement.
Corrections have thus been made to specify, for example, that the registration certificate (orange card) issued to a family member of a citizen of the Union is indeed a residence document that should be taken into consideration as proof of legal residence within the meaning of the Code of Belgian Nationality.
However, the royal decree implementing the Code of Nationality remains incomplete and will necessarily have to be adapted again.
First of all, Brexit has led to the creation of a new category of foreigners who must be in possession of an "M" (or "N" for cross-border commuters) residence permit: the beneficiaries of the withdrawal agreement and their family members. However, unless provided otherwise, the principle is that these persons are subject to the same rules, regarding residence, as those applicable to citizens of the Union and their family members (new Article 47/5, § 1, of the law of December 15, 1980 on access to the territory, residence, establishment and removal of foreigners, inserted by a law of December 16, 2020). It is therefore clear that M-cards are valid residence permits within the meaning of the Code of Belgian Nationality.
Secondly, with regard to taking special cards into account, if the Brussels’ French-speaking case-law and the practice of cases introduced in French had stabilized at the beginning of 2020 with the systematic taking into account of these cards, the same direction must now be taken for applications introduced in Dutch in Brussels, or in Flanders, at least for (ex-) citizens of the Union. Indeed, the Belgian Court of Cassation, finally deciding on the issue in a clear manner, recently indicated that the contrary would violate the above-mentioned Directive 2004/38.
Pending clarification from the legislator, the Belgian authorities must already comply with the international obligations that are directly imposed upon them. Thus, a municipality cannot refuse to register a declaration of nationality on the grounds that the person has an M-card or has had a special residence in the past. In the same way, a refusal by the Public Prosecutor with respect to such a request and on that ground would justify an appeal before the courts and would probably be contradicted in the light of the current case-law.