A state violates international law when it commits an “internationally wrongful act", which breaches an international obligation that the state was bound by at the time when the act took place.
International Law Commission’s Draft Article on State Responsibility
One of the major legal instruments referred to in the context of state responsibility is the International Law Commission’s (ILC) Draft Articles on State Responsibility for Internationally Wrongful Acts.
The articles intend to complement existing obligations in other sources of international law such as the Four Geneva Conventions, and they provide a general supplementary framework for the concept of state responsibility.
They answer the questions - when does a state violate international law, and what is its responsibility if it does?
After five decades of revision and negotiation, the Draft Articles were finally adopted by the ILC in 2001, and later the same year, the UN General Assembly adopted a resolution which “commend(ed the articles) to the attention of Governments without prejudice to the question of their future adoption or other appropriate action”. Although they do not constitute a legally binding convention that states must follow, many of the principles correspond to existing international law.
The Draft Articles are followed by commentaries that provide a tool for their interpretation.
The International Law Commission is a body of independent legal experts, which operate under the General Assembly.
Agreements must be respected
A State is bound to act in accordance with international customary law, and follow any international treaty it has signed and ratified. This is a fundamental principle in international law called “pacta sunt servanda” - agreements must be respected - which follows both from the Vienna Convention on the Law of Treaties, and international customary law. International humanitarian law (IHL) conventions and human rights treaties are examples of sources for a state’s international obligations.
Exceptional cases - no state responsibility
There are a number of exceptions when an act that normally would be a violation of international law, does not create responsibility of the state involved, such as cases of consent, self-defence or necessity (ILC Draft, Articles 20-26).
In IHL and human rights
The exceptions mentioned above are less relevant when it comes to human rights and international humanitarian law (IHL).
A state cannot give its consent to another state to commit violations of human rights or IHL towards its citizens.
A state cannot claim that there is a necessity to prevent civilians of benefits they are entitled to in IHL, such as protection against targeted attacks.
A state cannot claim self-defence to justify violations of IHL and human rights.