The article analyzes the issue of the statute of form in the context of lex fori processualis, focusing on evidentiary rules. The distinction between procedural and substantive rules in evidence law raises controversies, particularly in relation to the ad probationem form and foreign documents. The author discusses various doctrinal views on the legal nature of form regulations, analyzing their procedural and substantive aspects. It also addresses issues related to official documents and their legalization, especially in the context of entries in court registers.