This article seeks to illustrate how the Principles of Distinction and Proportionality, coming from a branch of primary rules (International Humanitarian Law) have a relevant influence on the modern system of international criminal responsibility, consecrated in the Statute of the International Criminal Court, ICC. It is found that even if the latter contains provisions –war crimes– reproaching conducts due to their indiscriminate character, there are gaps related with the meaning and extension of such criminal conducts; this problematic is explained on one hand, by the political reluctance of States to compromise their sovereignty, and the specificities of the punitive function on the other. Practical consequences can be seen on the way on which modern armed conflicts take place, as most of them take place in a non-international level. Despite of a pessimist diagnosis, it has to be firmly pointed that the sole fact that a permanent criminal court has came to be a reality is a tremendous gain, provided that it is through its activity i.e. the production of clarifying jurisprudence, that this problems will be confronted and solved.