Most contemporary armed conflicts are not of an international character. International Humanitarian Law (IHL) applicable to these conflicts is equally binding on non-State armed groups as it is on States. The legal mechanisms for its implementation are, however, still mainly geared toward States. The author considers that the perspective of such groups and the difficulties for them in applying IHL should be taken into account in order to make the law more realistic and more often respected. It is submitted that the law is currently often developed and interpreted without taking into account the realities of armed groups. This contribution explores how armed groups could be involved in the development, interpretation and operationalization of the law. It argues that armed groups should be allowed to accept IHL formally, to create – amongst other things – a certain sense of ownership. Their respect of the law should also be rewarded. Possible methods to encourage, monitor and control respect of IHL by armed groups are described. The author suggests in particular that armed groups should be allowed and encouraged to report on their implementation of IHL to an existing or newly created institution. Finally, in case of violations, this contribution proposes ways to apply criminal, civil and international responsibility, including sanctions, to non-State armed groups.