The paper addresses underexplored issues in legal theory, including legislative silence, closed legislative lists, and the «opening» of such lists through the application of the contra legem doctrine, as well as supplementing these lists via the extra legem doctrine. For purposes of terminological precision, the author identifies two manifestations of legislative silence (legislative gap): legislative omission and deliberate legislative silence. A legislative gap may result not only from omission but also from deliberate silence on the part of the legislature. The study proposes the concept of a presumption of legislative omission, whereby, in the absence of factual evidence of the legislature’s conscious decision not to regulate certain relations, one should proceed from a rebuttable presumption that such non‑regulation is the result of legislative omission (error). This presumption may be rebutted by factual evidence confirming the legislature’s deliberate silence. Where the presumption of legislative omission applies, the gap may be filled through the extra legem doctrine as a means of legal development. A different approach applies in the case of closed lists. Given the specific legislative drafting technique inherent in closed enumerations (an implicit prohibition on performing legal acts involving elements not included in the list), the author notes that closed lists operate under a presumption of deliberate legislative silence. If, in the case of closed enumerations, this presumption is not rebutted, the list may be «opened» in accordance with fundamental principles of law, incorporating a new element through the contra legem doctrine of legal development.