DNS is a listing of address resolution. Ignoring/Dropping records is not modifying existing entries/mappings. That's a different thing in my eyes.

If the ruling were to declare published content must not be modified, I think there's multiple levels to it too, and it may dictate to any degree between them.

1. Interpretative tools (like a screen reader would be, or forced high contrast mode), which may be classified accessibility too
2. CSS hacks that change display style but not what is shown (for example forcing a dark mode, reduced spacing, or bigger font sizes)
3. CSS hacks or ad blockers that modify or hide content (block ads that would otherwise be rendered)

The biggest danger for a "copyright violation" would be the last point. Given that styling is part of the website though, "injection with intent to modify" may very well be part of it too, though.

It certainly would go directly against the open web with all of its advantages.

/edit: Comment by manxu, who read the ruling, is a lot less alarming.