The Court of Justice delivered last week (2 June 2022) its judgment in Case C‑617/20 (T.N. and alii), which is about the Succession Regulation:

“Articles 13 and 28 of Regulation (EU) No 650/2012 […] must be interpreted as meaning that a declaration concerning the waiver of succession made by an heir before a court of the Member State of his or her habitual residence is regarded as valid as to form in the case where the formal requirements applicable before that court have been complied with, without it being necessary, for the purposes of that validity, for that declaration to meet the formal requirements of the law applicable to the succession”.

Source: https://curia.europa.eu/juris/document/document.jsf;jsessionid=D6263372CF35902864FE65D23613F425?text=&docid=260184&pageIndex=0&doclang=EN&mode=req&dir=&occ=first&part=1&cid=4507548