Answering the question of whether international law prohibits sexual violence by armed groups against child soldiers in their own ranks should be straightforward: it is prohibited. However, as seen in recent cases before the International Criminal Court (ICC), this is not necessarily the case. The present article critically discusses two approaches suggested in ICC jurisprudence, namely prosecuting sexual violence against children as constitutive of the war crime of ‘using [children] to participate actively in hostilities’ (Article 8(2)(e)(vii) of the ICC Statute), or directly as the war crime of ‘committing rape [or] sexual slavery’ (Article 8(2)(e)(vi) of the ICC Statute). First, it is shown that prosecuting sexual violence under the crime of using children to participate actively in hostilities is unconvincing. Abusing children for sexual purposes does not fall under the scope of active participation in hostilities. If it did, this could have the unintended consequence of depriving children of their civilian status and protection under other provisions of the ICC Statute and international humanitarian law (IHL). Second, it is argued that in the Ntaganda case the Pre-Trial Chamber (PTC) circumvented the question of whether and to what extent children may generally lose their civilian status and protection under IHL if they become member of a party’s armed forces. If children join armed groups or armed forces, the questions arise whether IHL addresses intra-party violence, and under what conditions such violence can be prosecuted as a war crime in non-international armed conflicts.