Terrorist acts may occur during armed conflicts or in time of peace. As international humanitarian law applies only in situations of armed conflict, it does not regulate terrorist acts committed in peacetime.

The requirement to distinguish between civilians and combatants, and the prohibition of attacks on civilians or indiscriminate attacks, lies at the heart of humanitarian law. In addition to an express prohibition of all acts aimed at spreading terror among the civilian population (Art. 51, para. 2, Protocol I; and Art. 13, para. 2, Protocol II), IHL also proscribes the following acts, which could be considered as terrorist attacks:

• attacks on civilians and civilian objects (Arts. 51, para. 2, and 52, Protocol I; and Art. 13, Protocol II);
• indiscriminate attacks (Art. 51, para. 4, Protocol I);
• attacks on places of worship (Art. 53, Protocol I; and Art. 16, Protocol II);
• attacks on works and installations containing dangerous forces (Art. 56, Protocol I; and Art. 15, Protocol II);
• the taking of hostages (Art. 75, Protocol I; Art. 3 common to the four Conventions; and Art. 4, para. 2b, Protocol II);
• murder of persons not or no longer taking part in hostilities (Art. 75, Protocol I; Art. 3 common to the four Conventions; and Art. 4, para. 2a, Protocol II).

Apart from prohibiting the above acts, humanitarian law contains stipulations to repress violations of these prohibitions and mechanisms for implementing these obligations, which are much more developed than any obligation that currently exists under international conventions for the prevention and punishment of terrorism.