Editing Ultimatum (section)

==International law==
The [[Hague Convention of 1907|Hague Convention]] relevant to the Opening of Hostilities of 18 October 1907, provides as follows: 

{{Blockquote|"Considering that it is important, in order to ensure the maintenances of pacific relations, that hostilities should not commence without previous warning," it is agreed by the Contracting Powers to "recognize that hostilities between them must not commence without a previous and explicit warning in the form of either a [[declaration of war]], giving reasons, or an ultimatum with a conditional declaration of war."}}

As reasons for a declaration of war are necessarily in the nature of an ultimatum, the ultimatum may now be regarded as an indispensable formality precedent to the outbreak of hostilities.

Another Hague convention of the same date respecting the limitation of the employment of force for the recovery of contract debts provides as follows:

{{Blockquote|"Being desirous of preventing between nations armed conflicts originating in a pecuniary dispute respecting contract debts claimed from the government of one country by the government of another country as due to its subjects or citizens," the Contracting Powers agree "not to have recourse to armed force for the recovery of contract debts claimed from the government of one country by the government of another country as being due to its subjects or citizens."}}

This undertaking, however, is not applicable when the debtor state refuses or neglects to reply to an offer of arbitration or, "after accepting the offer, renders the settlement of the compromise impossible, or, after the arbitration, fails to comply with the award."

Under this convention, in the cases that it relates, the alternative of the ultimatum is ipso facto arbitration, and it is only when the conditions of the convention have been set at naught that other measures may be employed.<ref>{{Cite EB1911|wstitle=Ultimatum}}</ref>

===Subsequent to the United Nations Charter===
The United Nations Charter<ref>Article 2(4)</ref> prohibits not only the [[use of force in international law|use of force]] but also the threat of such use of force, but there is discussion on whether this prohibition applies only to (militarily) credible threats, whether (or when) the threat of the use of force in self-defence is permitted, and what actions (not necessarily accompanied by a verbal threat) can be considered a threat.{{Sfn| Grimal |2012|loc=Introduction}} 
The [[International Court of Justice]] has provided guidance on the legality of the use of threats: generally, if the use of force would be lawful, the threat of such use of force is also legal, and if the actual use of force is later found lawful, then the prior threat is also deemed lawful.{{Sfn| Grimal |2012|loc=Introduction}}