My two cents is that based on the conversation Harry and Luccio have about the Laws, this is a really clear cut issue.
It doesn't matter who you are or where you're getting power from. Casting a spell means you believe in it. Breaking the Laws "breaks" free will, and the active, conscious choice to interfere with others' free will warps and twists your own self in the negative.
This is why I refer to the separation between metaphysical Lawbreaking and legal Lawbreaking. The White Council, through the Wardens, do their best to enforce Lawbreaking "legally" in an attempt to bring justice for those who metaphysically break the Laws. And like any legal system, it only approximates justice. Through this the White Council also somewhat polices irresponsible magic, which is why a Warden would be within his rights to chop off your head if you lose control of a practice evocation and you blow up your neighbor. You didn't mean to do anything, you didn't really do anything intentional to end someone's life, but you still killed them. Letter of the Law, and all that. Choppy choppy.
In the end, every situation that brings Lawbreaking into question brings two questions to the foreground. Instead of "are they a Lawbreaker," you have to ask, "Are they a metaphysical Lawbreaker?" and "Are they a legal Lawbreaker?" You can be neither, one or the other, or both. At the end of the day, the Council only cares/enforces whether you're a legal Lawbreaker. In the example above, you didn't mean to blow up your neighbor; you're not a metaphysical Lawbreaker. But the Law is clear, and you violated it, so legally speaking, Wardens are comin'.
So now we get into "so what if you use Seelie magic and you're a changeling?" type questions. If you're attached to another member of the Accords, then that Signatory is laying claim to you. The White Council can't touch you except through legitimate means via the Accords. They might request nicely, but they don't have real teeth, most of the time. Which is why Elaine sought Summer's protection. If you're not attached to a member of the Accords, but are attached to a Power, the White Council might choose to "look the other way" out of sheer desire not to go up against a hoary god. Or, for instance, a recently-kicked-out-of-the-Accords Denarian who breaks all sorts of Laws.
A note, changelings aren't by default "part of the Court." They are claimed sometimes, sometimes they aren't.
That said, if you're going around killing people with magic, breaking their minds, turning them into toads...you're still going to become a monster. Mortal is mortal, and we are told repeatedly that metaphysical Lawbreakers, those who willingly and purposefully abrograte another's free will change themselves in the process.
To be honest, I always thought this whole aspect of the books was a really striking insight into Jim's views on choice, free will, and morality (what makes one a monster?), but maybe that's just me.
