The laws of magic are far more spirit than letter of the law. The idea behind the Lawbreaker power is that your soul got twisted by a willful decision on your part. In other words, if either intent or hubris resulted in the law being broken, then you're a lawbreaker.
Here are some examples:
- You're facing down a couple of red court vampires in the middle of a plaza swarming with people. You turn around and blast them with your uber firebolt ... and lose control of the spell. You really want those vamps dead but don't want to risk taking injuring yourself, so you instead let loose some of the energy as fallout. And half the spell veers to the side and smokes a small child. BOOM, instant Lawbreaker! You weren't targeting the child, but your hubris caused you to not only use dangerous fire magic in the middle of a crowd, but let the out of control spell turn into fallout instead of backlash.
- You're facing down a couple of red court vampires in the middle of an empty plaza at 4 in the morning. You look around and see no one and have no reason to believe anything living is nearby. Run same scenario, but this time the fallout hits some homeless guy sleeping quietly in some bushes, hidden from view. There I wouldn't have hit the player with Lawbreaker, but depending on his actions afterwards, not to mention repeat occurrences, might do some later. Again, a question of hubris ... the first time was an accident, but several accidents in a row starts to smell pretty smug.
- SPOILER:
At the end of Grave Peril, Harry only releases the spirit of the dead trapped in Bianca's mansion. He didn't guide them or control them, he simply let them loose. That would not be a Lawbreaker as he simply open their jail cell and let their own free will run wild.
- SPOILER:
In Dead Beat, the Necromancers not only summoned human ghosts and controlled them, but then subsequently used them to kill. *Definitely* breaking the 5th law, and arguably the 1st as well. Mind you, Harry also zombified a T-Rex (proud member of the I Love Sue fan club!). First off, he brought forth an undead dinosaur, not a sentient and free willed being, so no Lawbreaker on the 5th there (although for dabbling, I'd possibly give it to him if it became a repeat occurrence), and he only threw Sue at other zombies, so no 1st there either.