This article examines the role of the law of neutrality, namely the international legal regime defining the status of a State not party to an international armed conflict, in the Russian-Ukrainian armed conflict by analyzing the legal justifications offered by States and scholars with reference to the provision of weapons to the belligerents. The findings reveal that different positions could be identified ranging from an approach that reflects continuity regarding the basic premises characterizing this legal regime, to the emergence of a relevant discontinuity regarding its traditional legal contours or, finally, solutions implying its current legal irrelevance, even if on multiple occasions States have refrained from framing their positions in clear legal terms. The diminishing relevance of the law of neutrality may eventually lead to a legal order where third-party involvement in conflicts becomes more common. At the same time, the ongoing crisis of the United Nations’ collective security system and violations of its basic principles might risk making traditional interpretations of the law of neutrality a legal component of the lawfare portfolio available to States violating the prohibition on using force, thus mandating a reassessment in its interpretation.