First, this seems to be treading closely to 'nastily surprise the character' territory.
But...obviously the first wizard gets Lawbreaker, unless the transformation was completely voluntary. (I suspect the Wardens would disagree, but I would allow free consent to trump Lawbreaker.)
Unless the second wizard had some way of knowing that what they were dealing with was once human, no Lawbreaker. No intent, and no way of knowing. And quite possibly, no longer a person at all.
This would make a far better story if the second wizard was investigating a possible warlock...and discovered a sick, angry, formerly human dog. Now they know the problem; what do they do?