The use of such weapons against a civilian population would potentially violate several international laws and conventions:

1. Geneva Conventions (1949) and Additional Protocols:

   • Article 3 common to the four Geneva Conventions: Prohibits "violence to life and person, in particular murder of all kinds" against civilians.
   • Additional Protocol I (1977):
     • Article 51: Prohibits acts or threats of violence the primary purpose of which is to spread terror among the civilian population.
     • Article 52: Requires parties to distinguish between civilian objects and military objectives, prohibiting attacks on civilians or civilian objects.
     • Article 57: Obliges parties to take precautions in attack to avoid or minimize civilian harm.

2. Convention on Certain Conventional Weapons (CCW):

   • If these weapons fall into the category of indiscriminate or excessively injurious weapons, their use might contravene the spirit of Protocols III (on Incendiary Weapons) and V (on Explosive Remnants of War), which aim to protect civilians from unnecessary suffering or indiscriminate effects.

3. Customary International Humanitarian Law (IHL):

   • Rule 1: The parties to the conflict must at all times distinguish between civilians and combatants.
   • Rule 14: Prohibits starvation of civilians as a method of warfare, which could be relevant if such weapons are used to destroy food sources or infrastructure essential for civilian survival.
   • Rule 70: Prohibits the use of weapons calculated to cause unnecessary suffering or which have indiscriminate effects.

4. Rome Statute of the International Criminal Court (ICC):

   • Article 8: Defines war crimes, including:
     • Intentionally directing attacks against the civilian population as such or against individual civilians not taking direct part in hostilities.
     • Intentionally launching an attack in the knowledge that such attack will cause incidental loss of civilian life or injury to civilians, which would be excessive in relation to the concrete and direct overall military advantage anticipated.

5. UN Charter:

   • Article 2(4) commits all members to refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the Purposes of the United Nations.

6. Arms Trade Treaty (ATT):

   • While not directly prohibiting the use of such weapons, it requires countries to assess if weapons transfers could be used to commit or facilitate serious violations of international humanitarian law or human rights law.

If these weapons cause widespread, long-term, and severe damage to the natural environment or are used in a manner that cannot distinguish between military and civilian targets, their use would be considered a violation of these laws. However, the specifics of the weapon and the context of its use would need to be thoroughly investigated to determine exact violations.