Josh, just me, but I don't see an issue here.

1. Guy claimed this was part of a Mazda offered "IMSA Performance Package." CoA determined it was limited production and disallowed it. The right call.

2. Even if the driver tried to argue it was legal via negative implication -- limited production spoilers are disallowed -- he'd still lose because of, as Greg indicates, "if it doesn't say you can." No rule allows him to fab up a spoiler.