*Sigh*
First of all incendiary weapons are not banned. They are banned from being used on civilians and you can't drop incendiary bombs on a location with a concentration of civilians.
What bans? The Stasi used Decomposition/Zersetzung, which was some form of X-Ray Laser, the Star Wars Program was ongoing until at least until 2010 in the US, The US deployed microwave weapons in the second invasion of Iraq, the Soviets put ruby and carbon-dioxide lasers as anti-ballistic and anti-satellite measures and sonic weapons in the form LRADs are used by law enforcement around the world.
None of those weapons made it into general use for one reason or another. Some didn't work well enough for more general use, others were just closed down on because some other less high tech solution worked just as well and was more easily mass produced, in the case of Decomposition it's not clear how much it was actually the effect of the laser and how much it was psychosomatic and LRAD are the only directed energy weapons that have entered general use.
There's also the anti-drone rifles showing up on Ukrainian battlefields on both sides, but those remain to be seen if they stay in military use.
The only IRL reason I could find that makes such weapons unacceptable is the inability to get them enough power on the battlefield for them to be used.
What no weaponizing space treaties are you talking about? And where in them does it say that such weapons can't be fielded on Earth?
When clearing a purely military installation with no civilians in it? No they would not. When hitting a housing block? Oh yes.
Laser weapons as far as I am aware are not banned and are more problematic because they have a shorter range than a bullet on most battlefields.
As in the moment someone starts using laser weapons smoke screens can be deployed to counter them. Hard.
Not really no. Anything short of a nuke that can kill the nurse that tended to a soldier hit with it a week later can be countered with CBRN measures and pretty well at that.
Laser pointers can't set a tank on fire. I've seen those Youtube videos where people build laser guns. They are always done inside a closed space on flammable materials. Show me a laser gun that can work trough smoke on a modern soldier's combat equipment and one that isn't simply countered by wearing fucking googles before I'll believe you that laser guns are actually a thing.
And no the fact that if you point enough laser pointers on a human they get burns doesn't count considering how much time it takes to get even to first degree burns with that.
War crimes usually concern themselves with civilian damage inflicted by military forces since a lot of the treaties are on either civilians being targeted or POW mistreatment.
No weapons are fully banned from being used on a battlefield, though nukes and other weapons of mass destruction are heavily disincentivized by MAD.
Fuck's sake
@Simon_Jester is outright wrong in his statement that weapons that hit beyond the horizon and do unpredictable amount of damage depending on their spread are banned considering how much cluster munitions turn up in modern wars and while froned upon in some circles are still used by most sides in conflicts when they can get their hands on them.
