In 1980 there was a Convention concerning human rights during wartime it was called Convention Conventional Weapons (CCW). The convention made a number of weapons illegal many of which lead to international law reform concerning warfare. One of the laws passed was a protocol called Protocol III on Incendiary Weapons. It effectively banned all incendiary weapons for combat purposes.
This means that with every fireball being thrown Mario is committing a war crime. But it gets worse. Mat Pat used thermite to prove that Mario is using that as his weapon of choice the only thing Mario would need to do to make it available underwater is to make it so that the fuse could be lit in a water proof setup for underwater use.
Now I submit to you that Mario is now using thermite underwater to kill his enemies. Well now he's damaging the coral reef. While there are no laws protecting the environment during war that only covers sanctioned and or official military action. Mario has had many occupations in his past. He's been a carpenter, a plumber ( on and off ), a civilian doctor just to name a few. However no career he's had has been with any armed forces. So I submit that his actions AREN'T sanctioned.
Meaning that on top of war crimes he's violating laws and statutes of the Environmental Protection Agency and those of the Environmental Protection Act. Including ( but not limited to ) the Clean Water Act (CWA). Making Mario a criminal guilty of torture, potentially killing off endangered species, and destroying natural environments. I hope Mario has a law degree from a reputable law school cause if not he's going to need a good attorney...........maybe even saul goodman