An excerpt:

First of all, you need to get evidence. One type of weapon that could conceivably have been used, and which is often used in urban warfare, is white phosphorus. White phosphorus is not a chemical weapon. It is used primarily as a smoke generating agent, which can also be used as a military incendiary. Phosphorus can cause burns and harm people if used accidentally or intentionally. It does not apply to chemical weapons, but falls under the existing ban on the use of indiscriminate weapons against civilians. And this, in any case, qualifies as a war crime,’ says Kosal.