The NYT's C. J. Chivers, embedded with the Army's Company B of the First Battalion, 26th Infantry, in the Korangal Valley region of Afghanistan reports WP was issued in a recent ambush of Company B.

"Farther back, at Company B’s outpost, a pair of Air Force noncommissioned officers was directing aircraft into position, while two 120-millimeter mortars were firing high-explosive and white phosphorus rounds at targets the platoon had identified."

http://www.nytimes.com/2009/04/20/world/as...

WP's use as an anti-personnel weapon is banned by the Geneva Conventions.

Further, the Army itself bans its use.

"The US Army Battle Book - Field Manual 100-3, published in 1999 by the US Army Command and General Staff College at Ft Leavenworth, KS <20>states in Section III (Fire Support) paragraph section 5-11 para b subpara iii that 'It is against the law of land warfare to employ WP against personnel targets.'"

http://www.fas.org/man/dod-101/army/docs/s...