The theoretical separation of jus ad bellum and jus in bello provides important protection during armed conflict. It guarantees that jus in bello will apply regardless of the cause of a conflict. However, this distinction has been challenged by the view that in some cases, a situation of self-defence may be so extreme, and the threat to the survival of the State so great, that violations of jus in bello may be warranted. The situation is compounded by the confusion of the principles of necessity and proportionality under jus ad bellum and jus in bello in both academic writing as well as the jurisprudence of international courts. The dangers of blurring the distinction will be elucidated by examining how jus ad bellum considerations have affected the application of jus in bello in armed conflicts between States and non-State actors.