One other thought that just occurred to me... Bajor signed a non-aggression treaty with the Dominion. All Bajorans were ordered off DS9. Major Kira delivered an official protest from the Bajoran government for not surrendering the station to Bajoran authorities. In light of these circumstances, you can't really blame the Dominion for launching an assault on the station. They were, in a sense, coming to the aid of their friends who had asked the Federation to reliquish control of their space station. If Starfleet used the attack on DS9 as justification for attacking the shipyards, they would be on pretty shaky ground.