General rule of thumb: if it's been banned, it's useless for the signatories. Ex: chemical weapons, but also biological weapons, land mines, and cluster munitions. Note that land mines and cluster munitions are still actively being used, especially in Ukraine, and the countries that signed onto the ban largely got rid of those systems well before the ban was signed.
It has. That's why countries don't have real chemical weapons anymore. They are easy to make (for an industrialized country), but they don't provide any real advantage when both sides in a war have access to them. They just increase misery for everyone involved.
The argument I've seen against their usefulness is that they only work against static militaries that don't have NBC training, and a modern military can already defeat threats like that without paying the political cost of using them.
They're not. They're effective against an unprepared adversary. Any real military will have anti-chemical-weapons tactics and protection.
So this happens: you douse a building with a gas, and then walk inside and get shot by defenders in gas masks. And by the way, you also will have to wear a gas mask yourself.
Still need a major supplier both the laser emitters and esp. the optics. The weapons will be a lot more expensive compared to conventional weapons, or any anti-riot weaponry.
Aside the sci-fi vibe, I could imagine James Bond esque - still quite hard to use, has to aim for the eyes, scatter can cause collateral damage, doesn't work in fog, rain, etc.
