The International Criminal Court for the first time found guilty and sentenced a perpetrator of gender-based crimes under international law. Moreover, it did so by defining a new crime of forced marriage, which was considered by the international criminal law as “other inhumane act.” In its judgements, the International Criminal Court dealt with the challenges based on violation of legality and non-retroactivity principles. Further, it dealt with distinguishing the crime from sexual-based crime of sexual slavery. It upheld that the forced marriage is distinctive crime from the sexual-based crimes like forced pregnancy, sexual slavery, or rape, and that the principle of speciality does not bar cumulative convictions. Regarding the definition of forced marriage, it is not necessary for its commission to conclude valid marriage and the crime itself is continuing one, thus not only the act of entry into marriage is considered as criminal, but the whole duration of forced marriage. The third chapter puts the present development of international criminal law in the broader perspective of attempts to prosecute gender-based crimes and to distinguish them from the sexual-based crimes. Author comes to conclusions that the gender has to be interpreted in a conservative way and more extensive understandings of gender would require revision of the Rome Statute. International Law Commission itself was not firm in answering what the current rules on gender are.