you had a written agreement (a contract) and he did not abide by that, I say it should be repaired to the agreed state for no charge, legal or not.
I had my windows tinted, all I did was sign a form saying I knew that that performed work was illegal and the glass shop would take no responsibility for anything.
They were fine with doing the work, and I was fine with signing the form.
I think I would talk to them again very calmly and ask for it to be repaired as per the work order. Then go above that person, to their boss and explain it to him and show him what was agreed to on paper.