Attacks perpetrated, since November 2023, by Houthis, in the Red Sea, against commercial and military vessels raise interesting questions on the qualification of the use of force. On-the-spot self-defence against Houthi armed attacks taking place in the high seas is lawful. Further action against inland Houthis revisits the much discussed admissibility of the use of force against non-State actors (under Article 51 of the Charter, self-defence is designed to be exercised against States) and the requirements of self-defence. The UN Security Council has been following the Yemeni civil war, but no authorisation was granted for the use of force against Houthis. No invitation to intervene was addressed by Yemen to any of the States claiming self defence against inland Houthis in response to recent naval attacks. Self-defence against inland Houthis, if unopposed by the territorial State, may be lawfully construed as an act against a de facto Government.