Before ratifying the 1977 Protocol 1 Additional (to the 1949 Geneva Conventions the UK issued a Statement of Understanding which stated that the UK did not accept that new parts of the treaty apply to nuclear weapons: "It continues to be the understanding of the United Kingdom that the rules introduced by the Protocol apply exclusively to conventional weapons without prejudice to any other rules of international law applicable to other types of weapons. In particular, the rules so introduced do not have any effect on and do not regulate or prohibit the use of nuclear weapons."
In 1995 the UK's oral statement to the International Court of Justice in the nuclear weapons case said much the same thing: "... any new provisions introduced into the law of armed conflict by the Additional Protocols would apply only to conventional weapons." but added "We fully accept, however, that the use of nuclear weapons is subject to the principles of customary international law, and it is plain that some of the provisions of Additional Protocol I did no more than reaffirm and codify principles of the customary law of armed conflict which already existed and which apply to the use of all weapons, including nuclear weapons." We can therefore assume that the sections of the Protocol we are concerned with are part of the pre-existing legal principles accepted by the UK.
Article 57/1 of Additional Protocol 1 says: "In the conduct of military operations, constant care shall be taken to spare the civilian population, civilians and civilian objects." Article 57 (iii) (Precautions in attack) says that states must "refrain from deciding to launch any attack which may be expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof, which would be excessive in relation to the concrete and direct military advantage anticipated."
Anyone launching a nuclear strike therefore has a duty of care as laid down in the Additional Protocol. A commander in the field, or his or her political superiors, would have to decide whether the immediate military advantage of a nuclear strike would outweigh the likely civilian suffering it would entail. This is the Principle of Proportionality. The commander has a Duty of Care to ensure that non-combatant casualties are minimised.
The UK sees the Duty of Care as a binding rule of IHL. The Manual of the Law of Armed Conflict, is the most authoritative possible expression of official UK opinion. It refers explicitly to the language of Protocol 1. Thus: "(5.32.1) Additional Protocol 1 lays down a general obligation on the parties to the conflict to take care in the conduct of military operations to spare civilians." and (5.32.1 .c) [those who plan or decide upon an attack shall]: refrain from deciding to launch any attack which may be expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof, which would be excessive in relation to the concrete and direct military advantage anticipated. [the rule of proportionality]
There is one final link in the argument. The claim in the White Paper that the International Court of Justice (ICJ) "rejected the argument that such use would necessarily be unlawful in all circumstances." is incorrect. In fact, the Court decided not to pronounce on the matter because it did not have enough information to formulate a ruling based on IHL.
" .....However, in view of the current state of international law, and of the elements of fact at its disposal, the Court cannot conclude definitively whether the threat or use of nuclear weapons would be lawful or unlawful in an extreme circumstance of self-defence, in which the very survival of a State would be at stake" Para 105, 7 (2) E.
A decision not to pronounce is not the same as a rejection. The President of the Court said that this "cannot in any way be interpreted as a half-open door to the recognition of the legality of the threat or use of nuclear weapons". (Judge Bedjaoui, Separate Statement, para 11).
