This article addresses a key legal debate that the Baltic NATO members ought to engage in: what constitutes an “armed attack” and what interpretation should be made of this concept in order to deter recent Russian hybrid warfare strategies. These questions are considered in connection with a more general issue regarding the law of self-defence: the question of what constitutes an armed attack in international law. This article will try to present a broad definition and context of Russian hybrid warfare and how it is challenging traditional jus ad bellum paradigms. Too few policy-makers have paid detailed attention to the new Russian “lawfare” in Ukraine, using specific military and non-military tactics in order to blur the lines between “armed attack” and mere political intervention. Meanwhile, legal scholars detach their analysis from actual policy-serving considerations and tend to acquiesce to some very restrictive theories of the use force in self-defence. For some countries, like the Baltic ones, facing strategic exposure – because of both threatening neighbours and low military capacities – the jus ad bellum paradigm should not be construed as another layer of obstacle.