在國際刑法學上，侵略戰爭罪是最具吊詭性的犯罪行為。一方面它被視為是國際社會中鍛嚴重的犯罪行為，對侵略戰爭罪加以嚴厲處罰的「正當性」鮮少被質疑過；但另一方面，對侵略戰爭罪的精確定義也從來不曾有過共識，也就是說侵略戰爭罪的「合法性」至今仍舊是個棘手的課題。甚至在一九九八年通過的羅為國際刑事法院規約中，其第九條第一項第四款雖有「侵略犯罪」這個標題，但其構成要件的內容卻是空白的，因利而國際刑事法院也無法對侵略犯罪行使管轄權。但至少可以說，將侵略戰爭視為國際刑法上的犯罪行為，不僅在聯合國大會中無異議通過；同時在國際法委員會的眾多草案中，也都明白承認此一犯罪構成要件，並最終納入於國際刑事法院規約，因此，侵略戰爭罪毫無疑問地已成為國際習慣法上所承認的犯罪行為。

The crime of aggression is the most paradoxical criminal offence in the International Criminal Law. On the one hand, it is deemed as the severest crime in the international society, the "legitimacy" of its severe punishment is rarely questioned. On the other hand, there is still no consensus for a precise definition on the crime of aggression, which means, the "legality" of its punishment is still an issue needed attention. Though "The crime of aggression" is clearly stated in the sub-paragraph d of paragraph 1 of Article 5 in the Rome Statute of the International Criminal Court passed in 1998, the content of this crime remains empty; therefore the International Criminal Court has no jurisdiction over the crime of aggression. But at least we can say, the aggression as a crime in the International Criminal Law is agreed in the United Nation's Assembly. And many documents drafted by the International La Commission of the U.N have admitted this crime, which also finally included in the Rome Statute of the International Criminal Court. Therefore, the crime of aggression is undoubtedly an admitted crime in the Customary International Law.