The topic of this article is the changing scope of the principle of non-intervention. Whereas the principle of non-intervention was previously honored as the most appropriate principle for the regulation of interstate relations, various concerns have recently been advanced as justifications for interventions. This suggests that the scope of the principle of non-intervention has gone through important modifications since the end of the Cold War. The scope for justified resort to force has expanded accordingly. The article has a double aim. First, I depict what seem to be emerging criteria for justified interventions. The UN Security Council practice of authorizing interventions suggests that states may lose their claim to protection under the principle of non-intervention if one or more of the following conditions have been met: (1) the state engages in systematic human rights violations; (2) it is incapable of protecting human rights violations due to breakdown of state authority; (3) the government in power is unlawfully constituted. When these conditions have been present, the Security Council has considered the situation a 'threat to the peace' and thus has the legal powers to authorize enforcement measures under Chapter VII. The second aim of the article is to discuss the danger that, by softening the principle of non-intervention, the UN may get on a slippery slope of forcible interference. One reason for resisting a softening of the principle of non-intervention is that once interventions are allowed for some normatively defensible purposes, it will be difficult to establish barriers against a further softening of this principle, which may eventually have intolerable consequences. I argue, however, that the slope of UN-authorized interventions is not that slippery after all. Consequently, the dangers of entering them in the first place are not overwhelming.