They denied using WP illegally in Gaza.

"The Israel Defense Forces (IDF) Thursday responded to accusations about Israel’s use of white phosphorus in Lebanon with a carefully worded statement, dismissing reports that the incendiary substance has been used for setting fires but conceding that it does use it in some circumstances."

https://edition.cnn.com/middleeast/live-news/israel-hamas-war-gaza-news-11-02-23/h_d86d7e2d45ad434b0a4ff433a92a6d6f

Note: I am not questioning the veracity of claims that they've used it illegally. I'm only addressing the false statement in the linked article. The IDF statement precedes the article by a month.

Under international law and the UN's Convention on Certain Conventional Weapons, WP is prohibited if it's part of an incendiary weapon and those weapons are used against civilian targets or military targets in civilian population areas. It is not banned otherwise and can be used as a smoke screen, etc.

In short, there's no ban on white phosphorus. Its use is restricted in incendiary weapons.

“On the one hand this means it can be useful for legitimate military purposes — like creating a smokescreen to cover troop movement,” Rebecca Hamilton, a professor of law at American University, told McClatchy News.

“But it creates horrific injuries — burns can go down to the bone, with wounds that may reignite when bandages are removed,” Hamilton, who specializes in international human rights law, said.

Why is it controversial?

White phosphorus is controversial because of its ability to cause severe harm to civilian populations, according to HRW.

When the substance ignites, it produces an intense heat of 1,500 degrees Fahrenheit, more than seven times hotter than the temperature of boiling water.



https://news.yahoo.com/white-phosphorus-why-controversial-israel-190453570.html

Lebensraum?

from the article:

The artillery shells photographed on Oct. 9 and included in the recent Amnesty report bear markings that indicate they were assembled and loaded at the Pine Bluff Arsenal in September 1991. According to a U.S. Army document cataloging types of ammunition, each shell contains 116 felt wedges soaked with white phosphorus. After being fired into the air, a charge within the shell disburses the wedges, which then ignite upon contact with the air and generate thick, white smoke that flows downward as they fall to the ground. When deployed by an artillery weapon, such as a howitzer, they can cover an area as large as a football field

As long as the fuse is set properly and ignites at the proper altitude, all the WP will have burnt off by the time the felt wedges hit the ground. The resulting thick smoke will make you cough but it is not WP, and it will not burn,