In 2011, as violence in Libya was escalating, the UN Security Council imposed a no-fly zone banning flights in the country’s airspace ‘in order to help protect civilians’. The no-fly zone was enforced by states authorized by the Security Council to do so.
7.1 What are they?
No-fly zones are areas of airspace where most aircraft are prohibited from flying. They have been established by the UN Security Council on a very small number of occasions to protect civilians from a party putting them at risk by air operations, and facilitate the delivery of humanitarian assistance. Although the objective of
no-fly zones is to protect civilians and create conditions conducive to humanitarian operations, they are a military operation, not a form of humanitarian arrangement.
No-fly zones may be established in the airspace of the state whose conduct led to their imposition. This was the case of the no-fly zones established in northern and southern Iraq in the 1990s, and in Libya in 2011. No-fly zones may also be established in the airspace of a state that is being attacked by the party whose flights are excluded. This was the case in Bosnia and Herzegovina in 1993.
7.2 What does the law say?
No-fly zones raise legal issues additional to the humanitarian arrangements discussed so far in this paper, relating to the rules regulating resort to the use of force. The establishment of a zone is of no utility unless there is a military capacity to enforce it. In Bosnia, for example, in 1994 NATO states shot down four Serbian aircraft. Reportedly this occurred after more than 1,000 previous violations of the zone.
But the mere establishment of a no-fly zone, even if it is not actually enforced, constitutes a use of force or a threat of force. This has legal consequences.
7.2.1 Compliance with the rules regulating resort to armed force
First, the establishment of a no-fly zone must comply with the law on the use of force. Article 2(4) of the UN Charter prohibits the threat or use of force against the territorial integrity or political independence of any state. There are two established exceptions to this prohibition: use of force is permissible if authorized by the Security Council, or if used in individual or collective self-defence. There is controversy over whether force is also justified in the case of extreme humanitarian emergency.
To date, the Security Council has established no-fly zones on two occasions: in Bosnia and Herzegovina in 1992, and in Libya in 2011. The establishment and enforcement of these zones was clearly justified under international law, having been ordered and authorized by the Security Council. There are divergences of view as to whether the no-fly zones enforced by the US, the UK and France over northern and southern Iraq in 1991 and 1992 were legally justified.
In the absence of a Security Council authorization, the establishment of a no-fly zone over the territory of a state would nonetheless be permissible if it had been requested by that state, for example to assist it to exercise its right of self-defence. This could have been the case had third states accepted Ukraine’s request in 2022 to establish a no-fly zone over its own territory to prevent Russian air operations.
7.2.2 Armed conflict between the state(s) enforcing the no-fly zone and the excluded state
A second consequence of the fact that a no-fly zone constitutes a use of force is that the states that are enforcing the zone may become parties to an armed conflict with the state whose flights are being excluded. The unwillingness to enter into a direct confrontation with Russia influenced states not to accept Ukraine’s request to establish a no-fly zone in its airspace in 2022.
7.2.3 Compliance with IHL
In addition to the rules regulating resort to armed force, states that are enforcing a no-fly zone must comply with IHL.
The first step in the implementation of a no-fly zone is usually the destruction or disabling of any ground-based air defence systems. When conducting such operations, states must ensure they comply with the rules of IHL regulating the conduct of hostilities, including taking constant care to spare civilians and not to impede humanitarian operations.
As for all military operations, the measures outlined in other chapters of this paper will be of relevance to the enforcement of no-fly zones – including humanitarian notification arrangements, and agreements to establish humanitarian corridors or temporarily suspend hostilities.
In addition, the establishment and enforcement of no-fly zones must not impede humanitarian operations; a part of their purpose may be indeed to facilitate such operations. As discussed below, arrangements must be established to allow humanitarian flights to transit through the no-fly zones.
7.3 Operation in practice – challenges, good practice and recommendations
A significant issue that has arisen in the implementation of no-fly zones is ensuring effective arrangements to allow humanitarian flights to transit through the zones.
The UN Security Council resolutions that established no-fly zones – in Bosnia and Libya – excluded humanitarian flights from the restrictions. In relation to Libya, for example, the Security Council resolution that imposed the no-fly zone excluded flights whose ‘sole purpose is humanitarian, such as delivering or facilitating the delivery of assistance, including medical supplies, food, humanitarian workers and related assistance, or evacuating foreign nationals from the Libyan Arab Jamahiriya’, or that are deemed necessary by the states enforcing the no-fly zone ‘for the benefit of the Libyan people’. The resolution also called for the establishment of appropriate mechanisms for implementing this exception.
In both cases, it was the multinational force that implemented the no-fly zones –
i.e. NATO, which also administered the processes for authorizing humanitarian flights.
Security Council resolutions establishing a no-fly zone should always include a broad, express exception for flights whose purpose is humanitarian. The arrangements for authorizing such flights adopted by the party enforcing the zone should be as light and efficient as possible, and should be communicated clearly at the outset of the operation.
7.4 In conclusion
No-fly zones can contribute to the security of civilians and the civilian infrastructure on which they depend, in situations when air operations are targeting them or are being conducted in an indiscriminate manner.
However, the decision to establish no-fly zones has significant political consequences, and the costs of enforcing them are extremely high. For these reasons it is an arrangement that is resorted to very rarely