Droning Bureaucrats

Droning Bureaucrats's ability affects all creatures with mana value equal to exactly X, regardless of whether they were on the battlefield at the time the ability resolved. For example, if the ability resolves with an X of 4, then Giant Solifuge is put onto the battlefield, the Solifuge can't attack or block that turn.

Wotc — February 01, 2006

If you use Droning Bureaucrats's ability after you have declared attackers but before your opponent declares blockers, the restriction will apply to only your opponent's creatures. Creatures that are already attacking will be unaffected.

Wotc — February 01, 2006

Creature lands and most token creatures have mana value 0. If a creature on the battlefield has {X} in its mana cost, treat X as 0.

Wotc — February 01, 2006