Member States may not collude to circumvent international law. Certainly Yemen and the US could have cooperated and presented their case in an attempt to obtain the authorization from the Security Council.
Oddly the US legal justification is not that their action complies with International Law, rather that International Law does not apply...instead the US' position is that "a conflict between a transnational non-state actor and a nation, occurring outside that nation's territory, is an armed conflict not of an international character." However, the US' legal position is rather short sighted, and just imagine how quickly such a legal paradigm would break down if any foreign nation ever attempted to bomb one of their own citizens residing in the US and then claimed such use of force was not of an international character; therefore, International Law is not applicable.
In another comment, you say the violation is a failure to "respect the sovereignty, territorial integrity and political independence of other States".
In the case of the US operations in Yemen we are discussing, the sovereignty, territorial integrity and political independence of Yemen have been respected, since the US had the permission and cooperation of the Yemen government. The territorial integrity and political independence of al-Qaeda in Yemen is certainly not being respected, but al-Qaeda is not a State.
>In the case of the US operations in Yemen we are discussing, the sovereignty, territorial integrity and political independence of Yemen have been respected
Again Yemen's consent/cooperation is not the litmus test. For example US/Afganistan, the US had Afganisttan's cooperation to use force against the Taliban; nevertheless, the US went to and obtained authorization from the UN Secruity Council. This is/was a legal requirement, irrespective of the consent of Afganistan. The reason the US did the lawful thing Afganistan and not Yemen, is due to a poor (self-serving) legal interpretation, where the US does not consider what it did in Yemen of international character but the US could not make the same argument for Afganistan. Essentially the US claims (in a legal sense) it can kill its own citizens anywhere in the world without international law applying because US believes such action is domestic in nature. In other words the US is not making your argument, that they can use force wherever a foreign nation consents, the US' position is that the can use force anywhere in the world (with or without consent) so long as the force is used against its own citizens.
AQAP is not a UN member. Yemen is at war with AQAP. Yemen allowed the US strikes. The US thus no more needs UN support to strike AQAP than it does to raid a Montana militia compound.
Unless I am mistaken the legal paradigm you seem to be suggesting is that one country can intervene in another country's domestic armed conflicts/civil wars so long as they are invited. Such a paradigm is exactly what the UN was established to prevent, unilateral military action. There are dozens of case studies from Africa in the past ~30 years alone, a given country breaks out into a civil war and the UN sends peace keepers or other countries send troops (typically always in cooperation with the established government) but they can not lawfully engage unless the UN has authorized the use of force or they act in self-defense.
>Yemen allowed the US strikes. The US thus no more needs UN support to strike AQAP than it does to raid a Montana militia compound.
Not even the US suggests this is the case, as you have expanded the use of force to non-citizens. The US' legal memo is very clear, the US believes they were allowed to Use Force in Yemen without UN authorization because the target was a US citizen making this a domestic issue. The US legal opinion was very narrow regarding use of force against a US citizen, anywhere in the World, but the legal opinion acknowledges if it was not a US citizen that International Law would apply.
The case where one country cooperates in a military effort with another country on that country's own soil is the opposite of a "unilateral military action". The word "unilateral" means one party.
Yes, doing something unilaterally also means it's done without the agreement or participation of other people it might affect. In this context any use of force outside self-defense or authorized by the UN is unilateral. Take for example, US going into Iraq, even though there was a "coalition of the willing" comprised of approximately 30 nations, generally the international community condemned the use of force as unilateral military action because it was not authorized by the UN.[1] While the UN retroactively authorized the use of force in Iraq, it is still viewed as unilateral in the eyes of the international community, where unilateral military action is defined as "non-Security Council authorized". [2]
The parties involved in the UN are member states. AQAP is not a member state. ISIS is not a member state. The KKK is not a member state. The Donetsk separatists are not a member state. None of these organizations can demand any kind of due process from the UN. The UN exclusively governs relationships between its members. The UN is by design not a "World Court" to which arbitrary parties can appeal.
The only two member states with standing in the AQAP conflict are Yemen and the US. Both members agree on the action. Similarly, the US doesn't need the permission of the UN Security Council to raid the compound of a Montana militia group.
The UN Security Council is simply not implicated in the conflict with AQAP in Yemen.
Should Yemen withdraw its permission for the US to use air resources to combat AQAP in Yemen, that would change.
We aren't discussing the US invasion of Iraq, nor is the premise of this discussion that the US has never skirted the UN; clearly they have, just as Russia did in the Ukraine, the UK did in the Falklands, Turkey did in Cypress, and so on. So it does your argument no good to point out that the US has in the past not respected the UN. That has no bearing on the situation in Yemen.
Oddly the US legal justification is not that their action complies with International Law, rather that International Law does not apply...instead the US' position is that "a conflict between a transnational non-state actor and a nation, occurring outside that nation's territory, is an armed conflict not of an international character." However, the US' legal position is rather short sighted, and just imagine how quickly such a legal paradigm would break down if any foreign nation ever attempted to bomb one of their own citizens residing in the US and then claimed such use of force was not of an international character; therefore, International Law is not applicable.