I believe white phosphorus is indeed covered by the Hague and the Geneva Protocol*, because it, you know, sets people on fire. However, it CAN be used on equipment - to burn down blockades and destroy munitions, so some soldiers have been known to use whi-pho to ignite equipment that people happen to be wearing.
And when it gets publicised, they don't generally get away with it.
But in general, the funny thing about these restrictions is that they only apply to military use against other signatory countries - hence police tend to use hollow point ammunition but the military is not allowed to. Similarly, if you're fighting against someone who uses mustard gas and all that, then you can theoretically unleash ebola-zombies against them. In theory.
At any rate, the idea of a gay-bomb is just funny - even the name.
*Different from the Geneva Conventions