The Laws of Magic are enforced by the White Council. They can enforce them against their own members, obviously. They can also enforce them against your average sorcerer, mortal practitioners who aren't members of the White Council, because they have no other Accords nation representing them - the White Council claims jurisdiction and nobody powerful is contesting that claim.
Fix the Summer Knight is a member of the Summer Court, an Accords nation. The White Council enforcing their internal laws against him just isn't going to fly.
I agree with that interpretation too.
In my other thread about Mab and the Council, Knightedbishop posted,"[Carlos] understood [Molly] was now the executive of a sovereign nation."
I think the Knights are treated like citizens of a sovereign nation, so the council leaves them alone. Harry might be screwed because he was and still is a wizard, so the council can claim jurisdiction over him.
I think Snark Knight made a similar point above.