Whether they have the right or not doesn't much matter. They have the power to do it and no one realistically is going to stop them. Just like no one really did anything about Israel going into another country and kidnapping Adolf Eichmann. Some countries may shake their finger at the US as they did with Israel in that case but no real action will or can be taken. Rights are artificial constructs. If you don't have the right to take or have something, you invent one.
That's exactly what I was going to write. Therefore, kidnapping a terror suspect has legal precedent.