The principles of international humanitarian law, particularly of military necessity, distinction and proportionality all apply when any military action is considered during an armed conflict. 

Additional Protocols I and II to the 1949 Geneva Conventions contain specific provisions dealing with attacks on nuclear power plants.  Article 56 of Additional Protocol I specifically prohibits attacks against nuclear power plants. 

However, this is a qualified prohibition, if the facility is known to provide electricity also for military operations and if attacking it is the only way to shut off the power supply it can be attacked, although there remains a requirement to protect the civilian population. This prohibition is repeated, without any reservations, in Article 15 of Additional Protocol II, applicable in non-international armed conflicts, which states:

Works or installations containing dangerous forces, namely dams, dykes and nuclear electrical generating stations, shall not be made the object of attack, even where these objects are military objectives, if such attack may cause the release of dangerous forces and consequent severe losses among the civilian population.

Also, these Protocols consider nuclear power plants alone, not other types of nuclear facilities such as spent-fuel interim-storage sites, spent-fuel-reprocessing plants, high-level-waste repositories, and research reactors, which could also lead to harm to civilian populations. 

The 1996 African Nuclear-Weapon-Free Zone Treaty, commonly known as the Pelindaba Treaty also prohibits attacks on nuclear facilities. In addition, the Agreement on the Prohibition of Attack against Nuclear Installations and Facilities between India and Pakistan also prohibits attacks on each other’s facilities. 

The IAEA General Conference has explicitly declared that attacks against peaceful nuclear installations are prohibited under international law in a number of resolutions, including GC(XXVII)/RES/407 (1983);  GC(XXIX)/RES/444 (1984); and GC(XXIX)/765/Rev.1 (1985). More recently, similar resolutions have focused on the situation in Ukraine explicitly (GC(68)/8)

In July 2024, the UN General Assembly adopted a resolution (A/78/L.90) calling for the “immediate cessation of the attacks by the Russian Federation against critical energy infrastructure of Ukraine” and demanded “that the Russian Federation urgently withdraw its military and other unauthorized personnel from the Zaporizhzhia nuclear power plant” and return the plant to Ukrainian control.