When may a state lawfully invoke necessity as a circumstance precludingwrongfulness?

A state may lawfully invoke necessity as a circumstance precluding wrongfulness under international law in the following situations:

1. Grave and Imminent Peril: The state must be facing a grave and imminent peril. This means that the situation must be so severe that it threatens the essential interests of the state.

2. No Other Reasonable or Lawful Means: The state must have no other reasonable or lawful means to safeguard its essential interests. This means that the state has exhausted all other possible options and the only way to protect its interests is by invoking necessity.

3. Non-Contravention of an Obligation: The act must not seriously impair an essential interest of the state or states towards which the obligation exists, or of the international community as a whole. This means that the act of invoking necessity must not violate any obligations the state has towards other states or the international community.

4. Non-Creation of the Situation: The state must not have contributed to the situation of necessity. This means that the state cannot invoke necessity if it has played a part in creating the situation that it now claims necessitates its actions.

5. Proportionality: The act must be proportionate to the peril. This means that the actions taken by the state must not exceed what is necessary to safeguard its essential interests.

It's important to note that the invocation of necessity is a very exceptional circumstance under international law and is subject to strict conditions. It is not a carte blanche for states to act as they please.