Necessarianism, specially as espoused by Joseph Priestley.
A principle wherein a normally unlawful act is justified by the requirement of keeping one thing of better utilitarian price than that lost or sacrificed; not to ever be confused with self-defence.
The concept that, in a situation of crisis or exigent scenario, circumstances may legitimately work in many ways that could normally be illegal.
The principle the regulations of an illegal government is deemed valid insofar as they don't oppose the constitution, justified regarding basis that maintenance of government is of greater utilitarian value than maintenance regarding the law.
The concept that a state in instant peril to its existence, from a scenario maybe not of its own doing, may in extremis be justified in breaking a right of another state.