User blog comment:Omega natsu2/Episode 193: Seven Dragons, Review./@comment-25080404-20140803055709/@comment-4829046-20140803064028

Nah, it is all about judging the enemy. In this case the enemy is vague. All the info he got was that Dragons were invading the country and that the Kingdom had prepared a weapon that would eliminate most of them. I still think he could've used it though but they realized that only DS magic works. The anime expanded it with a lot more strategy so it seems long but in the manga it was fast-paced. Atlas Flame didn't just stand there roaring and posing before giving his speech and Makarov started the beat-down rather quickly so the "only DS magic works" revelation actually popped up rather quickly meaning that Fairy Law wouldn't work either since it was never mentioned to have been effective on Dragons.