Tayloria is an Asian country which has for many years maintained a distantrelationship with the West. Tayloria's leader is widely believed to be interested in developing nuclear weapons capability and Western intelligence reports suggest that Tayloria will be able to achieve this objective in the course of the next two years. The leader of Tayloria, whose behaviour is often characterized as eccentric in the Western media, has signed a bilateral mutual assistance treaty with the leader of Irvinia, a powerful country which already possesses nuclear weapons capability, but which has had a cordial relationship with most Western powers for more than a decade. The bilateral treaty indicates in part that "anattack on either of our countries will be deemed to be an attack on the othercountry", and that "any attack on Tayloria will give rise to the right of collectiveself-defence by Irvinia, andvice versa".

Hegemonia, a major industrial power which has had nuclear weapons capability for over 50 years, sends a memorandum to Tayloria warning that country toabandon its nuclear programme, but Tayloria responds saying "leave us alone;like you, wewill have nuclear weapons if we wish!" Hegemonia calls upon the United Nations Security Council "to take all necessary measures against Tayloria," but the draft Security Council Resolution to that effect is vetoed byPrestonia, a permanent member of the Security Council that has recently sold non-nuclear weapons to Tayloria.

Hegemonia launches a series of military strikes against Tayloria, arguing thatthis action will not affect the "territorial integrity or political independence ofTayloria as we donot propose to change the Government of Tayloria." Troopsfrom Tayloria respond with military action, and Irvinia sends troops into Tayloriato help them resist "the imperialists of Hegemonia."

During the fighting, 10,000 people are driven from their homes, and approximately 5,000 civilians are killed in the period of one month. Arguing that"the grave human rights abuses and murders in Tayloria shock the conscience of mankind", Nuffness, a third State also sends troops into Tayloria. Nuffnessmaintains that it has also acted to protect the lives of 500 nationals of Nuffnessliving in Tayloria and "to reinforce the doctrine of Responsibility to Protect in Customary International Law". Nuffness has no treaty with Tayloria and hasreceived no request for assistance from Tayloria.

Assuming that none of the States is party to any nuclear non-proliferation treaty, fully assess the lawfulness of the use of force by each State.

This question deals with Public International Law, and the Use of Force against States.