Pundits may credit Yahoo CEO Jerry Yang’s bullheadedness with scaring off Microsoft for the moment, but it appears that a tiny, yet timely, legal maneuver by Yahoo’s lawyers also played a key role.

On Saturday, Microsoft walked away from its three-month pursuit of Yahoo after leaders of the Sunnyvale, Calif., Internet company wouldn’t bite at a two-dollars-sweeter, $33-a-share offer. They apparently wanted $37 a share.