Shields block teleportation. Though I feel like having shields over all your major cities all the time is also going to pose a problem in and of itself. And SG teleportation breaks down your structure to base molecules, then reconstitutes you at the destination. Block the sensors, block the teleport, but that will also kinda ruin your own ability to use sensors too. 

It's not just the teleportation that I'm talking about, but the fact that you already claimed infiltration is flat out impossible because psykers. That effectively kills any attempt at espionage or covert actions against your faction, because they can just use mind powers to see through any possible subversion or infiltration or cloaking that I might have to use in whatever plots I develop. 

Also, I feel like teleporting a world destroying weapons to Ba'als quarters would, y'know, destroy the world. Which effectively ruins the point of fighting over the planet because you just blew it up.