Amid India-Pakistan Tensions, What International Law Says About War
A Closer Look at What Global Rules Say About War and Accountability
May 8, 2025
As tensions rise between India and Pakistan, questions about what constitutes a lawful war are once again in focus. International law makes a clear distinction between jus ad bellum (the right to go to war) and jus in bello (the rules governing conduct in war). These are framed by the United Nations Charter, customary international law and treaties such as the Geneva Conventions, all of which define what states and their leaders can—and cannot—do during conflict.
The Legal Grounds for Going to War
Under jus ad bellum, war is only lawful under two conditions: when it is in self-defence following an armed attack (as per Article 51 of the UN Charter), or when explicitly authorised by the UN Security Council under Chapter VII. Any war waged outside these parameters is considered an act of aggression and illegal under international law. The 1974 UN General Assembly Resolution 3314 defines aggression to include invasion, bombardment and occupation, and states that no justification, political or otherwise, excuses it.
A recent and clear-cut example is Russia’s 2022 full-scale invasion of Ukraine. Although Moscow labelled it a “special military operation” and claimed it was protecting Russian-speaking populations, Ukraine had not carried out any armed attack. The UN General Assembly passed several resolutions calling the invasion a violation of Ukrainian sovereignty, and the International Court of Justice ordered Russia to suspend military operations.
The Grey Zone of Pre-Emptive Self-Defence
International law is even stricter about pre-emptive self-defence—attacking based on a potential future threat. This is only lawful if the threat is imminent, overwhelming and allows no time for deliberation. Even then, it is contentious and subject to global scrutiny.
The 1967 Six-Day War is one of the most debated examples. In the lead-up, Egypt expelled UN peacekeepers from Sinai, massed troops along Israel’s border and closed the Straits of Tiran. Israel, claiming an imminent threat, launched a pre-emptive airstrike on June 5. Whether this qualified as lawful anticipatory self-defence remains disputed. Some legal scholars cite the blockade and military posture as legitimate threats. Others argue that Israel’s strike did not meet the Caroline doctrine’s strict standard: the threat must be “instant, overwhelming, and leaving no choice of means and no moment for deliberation.”
Rules for Conduct During War
Once conflict begins, jus in bello applies—regardless of whether the war itself is legal. Codified in the Geneva Conventions of 1949 and their Additional Protocols, this branch of law protects civilians, medical staff and aid workers, and regulates the conduct of hostilities.
Proportionality and Civilian Harm
A core principle is distinction: parties must distinguish between combatants and civilians. Targeting civilians or civilian infrastructure not used for military purposes is strictly prohibited and can amount to a war crime. Another principle is proportionality: even when targeting a military objective, civilian harm must not be excessive relative to the expected military advantage.
A case in point is NATO’s 1999 bombing of the Radio Television of Serbia (RTS) headquarters in Belgrade. Sixteen civilians, including journalists and technicians, were killed. NATO claimed the building served the Milosevic regime’s propaganda machine. However, critics, including Amnesty International, questioned whether the military value justified the known civilian loss—especially since the building had no role in military communications and the attack was carried out at night.
Weapons and Tactics That Are Off-Limits
International law also bans weapons that cause unnecessary suffering or are inherently indiscriminate—such as chemical and biological weapons. Torture, abuse of prisoners, hostage-taking and attacks on hospitals or religious sites are also prohibited unless those sites are used for military purposes.
One of the starkest examples is the 2013 Ghouta chemical attack in Syria. On August 21, rockets filled with sarin gas hit rebel-held areas near Damascus, killing hundreds of civilians, including many children. Multiple investigations, including by a UN mission, confirmed the use of sarin. While the Syrian regime denied involvement, evidence pointed to forces loyal to President Bashar al-Assad. Chemical weapons are banned under the 1925 Geneva Protocol and the Chemical Weapons Convention, both of which prohibit their use under any circumstances.
Further, nuclear weapons, though not banned outright under a universal treaty, are heavily restricted by international law. The International Court of Justice stated in 1996 that their use would violate humanitarian law principles like distinction and proportionality, though it left a narrow exception for extreme self-defence. The Treaty on the Prohibition of Nuclear Weapons outlaws their use, but neither India nor Pakistan has signed it. While both countries are also outside the Non-Proliferation Treaty, any use of nuclear weapons—given their indiscriminate impact—would certainly breach the laws of war and trigger major global condemnation.
The most recent—and only—use of nuclear weapons in armed conflict was in August 1945, when the United States dropped atomic bombs on the Japanese cities of Hiroshima and Nagasaki during World War II.
Accountability: When Leaders Are Prosecuted
International law also assigns individual criminal responsibility. Under the Rome Statute of the International Criminal Court (ICC), political leaders, military commanders and even rank-and-file soldiers can be prosecuted for war crimes, crimes against humanity and genocide—regardless of whether the state itself authorised the acts.
One precedent-setting case is that of former Liberian President Charles Taylor, convicted in 2012 by the Special Court for Sierra Leone. Although not an ICC trial, the case demonstrated that heads of state are not immune. Taylor was found guilty on 11 counts, including murder, rape and the use of child soldiers, for aiding the rebel group RUF during Sierra Leone’s civil war (1991–2002) in exchange for “blood diamonds.” He was sentenced to 50 years in prison.
Neutrality and the Dangers of Violating It
Neutrality laws place strict limits on third-party states. Neutral countries must not allow their territory to be used for military operations, and warring states are prohibited from carrying out attacks there. Violating neutrality can escalate war and draw in new parties.
One historic example is Germany’s invasion of Belgium in August 1914. Belgium’s neutrality had been guaranteed by the Treaty of London (1839). But Germany, seeking a route to France, invaded anyway. The U.K., citing its treaty obligations, entered World War I shortly afterward.
These examples show that international law does not just regulate whether war can be fought—it dictates how it must be fought, by whom, and with what limits. Even in war, law still applies—and breaking it brings consequences, or at the very least, global condemnation.
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