International rules exist that aim to protect the rights of civilians, combatants and detainees during violent conflict.
These laws are codified in a series of Geneva Conventions that provide a blueprint for trialling war criminals after the war is over.
There are 196 nation states that are party to the Geneva Conventions, and these form a major part of International Humanitarian Law – or the Humanitarian Law of Armed Conflicts – whose purpose is to provide minimum protections, standards of humane treatment, and fundamental guarantees of respect to individuals who become involved in conflict and war.
- In pictures: Up close with weapons being used on Ukraine frontline
- Sweden and UK: A military firepower comparison
- Russian losses explained: retired general says one-third of ground forces reduced
Is war legal?
The short answer is no. The role of enforcing international law broadly falls to the Security Council of the United Nations and the United Nations Charter, the founding document of the UN which aims to maintain international peace and security and uphold international law among its 196 member states, prohibits the use of force by one state against another.
But there are two exceptions:
- When the security council has approved the use of force
- When a state has a legitimate claim for self-defence
Since the end of the Second World War, declaring war in the traditional sense has become uncommon, limited to conflict areas in Western Asia and East Africa.
On 24 February, at 3:58 am, in a televised speech addressed to the Russian nation, President Putin announced that he made the decision to invade Ukraine.
It might seem like his speech was akin to declaring war, yet he called the invasion a 'special military operation'.
In Russia, it is illegal to call the war in Ukraine a war. Within the borders of the largest country on earth, referring to the invasion as a war and not a 'special military operation' can lead to imprisonment for up to 15 years.
The president's speech was broadcast at the same time as the UN Security Council was imploring him to stop. After eight bloody years of conflict, the invasion of Ukraine had officially begun.
In the speech, Putin said his country's actions were self-defence. The Kremlin's actions received worldwide condemnation immediately, the consensus from world leaders being that the claim to 'self-defence' was illegitimate.
Russia is a permanent member of the UN security council and has veto power, which holds back the UN from passing a resolution condemning its aggression.
Still, a large majority of nations condemned Russia's actions at the UN General Assembly.
In theory, there is an international prohibition on the use of force – in practice, it does not work. Moreover, when the use of force is applied illegitimately there is often no legal path to prosecution.
Among a worldwide outcry and verbal condemnation, individuals can get put on trial in The Hague for war crimes, while states are sanctioned.
What makes war illegal?
Less than a century ago, the world order which we take for granted today did not exist.
War was legal and the Paris Peace Pact of 1928 outlawed it for the first time in history. Within a year nearly every country in the world signed it, marking the first time in history that war was made illegal.
The generally accepted definition of war within academic circles is that 'war' is a violent conflict that claims more than 1,000 lives. According to this definition, the world has been at peace for only 8% of recorded history.
As a legitimate form of statecraft, war was heavily relied upon by heads of state to pursue national (and personal) interests. Being at war was the norm, before the Paris Peace Pact, a person could expect their country to be invaded or conquered at least once in their lifetime.
Today violent conflict is generally regarded as a moral abomination, a catastrophe to be avoided whatever the cost. In our time, land grabs and full-scale invasions are so rare, that when they happen, they are shocking to everyone but the aggressor.
The pact was signed in 1928, a mere 11 years before the start of the biggest and deadliest war the world had ever seen. The Second World War involved more than 30 countries and took the lives of more than 40 million.
The rules of war
Formally known as international humanitarian law (IHL), the rules of war are a set of rules that outline what can and cannot be done during war.
The rules of war are based on the international laws outlined in the Geneva Conventions.
The Geneva Conventions are a set of four treaties and three additional protocols, with the first Geneva Convention dating back to 1864.
Signed by 196 countries, the international treaty is applied universally around the world.
The Geneva Conventions aim to limit the suffering caused by war to non-combatants. Civilians, prisoners of war, health, and aid workers should not be targeted.
There are also rules of war that predate the Geneva Convention, known as the Geneva Protocol, which was signed in Switzerland in 1925.
The protocol outlaws the use of chemical and biological weapons such as phosphorus and chlorine gas.
The rules outlined in these international treaties are the reason why war tribunals are able to exist post-war and war criminals can be punished for their crimes against humanity.
What are the rules?
Henri Dunant, the founder of the Red Cross, campaigned to enshrine the rules of war for the first time in the Geneva Convention in 1864. At the time 12 countries signed on the dotted line.
The first treaty was primarily concerned with securing the right of prisoners of war, outlining that they must not be abused and outlining that armies have a legal duty to take care of the sick and wounded on the battlefields.
After the horrors of the First and Second World Wars, the subsequent Geneva Conventions expanded to include the treatment of civilians in war. Here is a summarised list of the rules of war:
- The targeting of civilians is a war crime. Those that are not fighting, such as medical, personnel, aid workers and ordinary people who have been caught up in conflict, must be protected.
- Prisoners of war must be treated with dignity. The humane treatment of detainees prohibits torture or degradation. There are no exceptions to this rule. The rules of war prohibit torture of any kind even if it would mean saving lives. Prisoners must be provided with food and water and be allowed to communicate with their loved ones.
- Medical workers care for the wounded on both sides of the conflict. They have to be protected. This includes the prohibition on targeting hospitals, as well as civilian buildings. However, the exception is that if a military objective has moved into a hospital then it is no longer a civilian structure and can be targeted.
- Rape and sexual violence is forbidden.
- To avoid unnecessary suffering and damage to the environment, the type of weapons that can be used in war are limited. Chemical and biological warfare are outlawed.
Does international humanitarian law apply to outer space?
The United Nations hosted an open-ended working group on reducing space threats at the beginning of May 2022, which aimed to promote the norms, rules and principles of responsible behaviours among countries that operate in space and those planning operations in space.
The group discussed whether existing regulations, including those set out in the Outer Space Treaty, were enough to regulate the risks and security associated with all activities of nations operating in space.
There have been calls to clarify how international law might regulate an armed conflict that starts in space or spills into outer space, given the growing technological advances that could potentially utilise space for military purposes.
While Article IV of the Outer Space Treaty states that the "moon and other celestial bodies shall be used by all States Parties to the Treaty exclusively for peaceful purposes", there have been questions within the UN and humanitarian organisations as to whether the treaty goes far enough to regulate in terms of potential conflicts spilling into the space domain.