Inaccurate?

Undeniable Gravity

(Miniatures Handbook)

Transmutation
Level: Bard 2, Sorcerer 2, Wizard 2,
Components: V, S, M,
Casting Time: 1 standard action
Range: Long (400 ft. + 40 ft./level)
Target: One flying creature
Duration: 1 min./level
Saving Throw: Will negates
Spell Resistance: Yes

A flying creature, which can be a creature that can fly by means of the fly spell or some similar magical effect, is grounded.
If this spell is cast on a creature currently flying, that creature descends at a speed of 60 feet per round but does not fall (and thus is not subject to falling damage).
The creature can still use its fly speed to move horizontally or down, but not up.
Once it is on the ground, the subject can no longer use its fly speed.
This spell does not affect incorporeal creatures.
Material Component: A wing torn from a fly.