Adopted in 2013 by the UN General Assembly, the Arms Trade Treaty sets international standards for transfers of conventional weapons, and addresses diverging security, geopolitical, economic and ethical interests related to the international arms trade. Why was it negotiated in the framework of the UN? How did the actors, notably the United States, pursue their interests? What are the treaty’s impacts? How does it affect the decision whether to supply lethal weapons to conflict areas such as Ukraine or Syria? What role will the United States play in the future?