No, use of the saliva is not a law breaker offense. It's not "magic", he is not a magic user, and not under the purview of the White Council.
But I'm not sure if a Changeling, or somebody like Fix who becomes a Faerie Knight without previous spellcasting ability, using raw Seelie or Unseelie Magic, would get Lawbreaker stunts or not. Again, I don't think the Wardens would get involved (they might conceivably mess with a Changeling who didn't have "backing" from their parent's Court, I guess)...
Sponsored Magic is a trickier case. When Harry's adding Hellfire or Soulfire on as basically a supercharge to magic he already has, it can clearly break the Laws.
But I'm not sure if a Changeling, or somebody like Fix who becomes a Faerie Knight without previous spellcasting ability, using raw Seelie or Unseelie Magic, would get Lawbreaker stunts or not. Again, I don't think the Wardens would get involved (they might conceivably mess with a Changeling who didn't have "backing" from their parent's Court, I guess)...