(Warning: this post contains opinions stated as if they were facts, because it's easier to write that way. Please respond as if everything had a "This is how I'd run it, but your table may find some other answer appropriate" disclaimer.)
First: Yes, that's lawbreaker - if and only if the assistant actually helps cast the ritual; someone merely contributing consequences or mundane setup (maneuvers for taggable aspects) would not get lawbreaker. As the book says, results, in the end, matter more than intent; you'd also get lawbreaker if you helped cast a ritual intended just to break a drought, and it caused casualties due to flash-flooding. However, I as a GM, would not put a PC in the position of getting lawbreaker accidentally or through trickery; that's just meta-game rude.
Second: Grey area. I wouldn't grant a lawbreaker power for this - but I would allow any appropriate existing lawbreaker powers to provide their bonuses, and I'd have the Wardens get very... concerned... if they ever found out about it.