, : Each creature with converted mana cost X can't attack or block this turn.
2/1/2006 Droning Bureaucrats’s ability affects all creatures with converted mana cost 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.
2/1/2006 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.
2/1/2006 Creature lands and most token creatures have converted mana cost 0. If a creature on the battlefield has in its mana cost, treat X as 0.