If I am not mistaking you are based in Switzerland, while Sony sued in Germany. For me the legal system is honestly a little bit of a mystery when multiple countries are involved, and it is hard to follow due to how many different rules can apply.
But Quad9 moved from that same jurisdiction in Northern California to Switzerland, and three days later, Sony attacked. Because of something called the Lugano Convention.
https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CEL...
The Lugano Convention is a spectacularly ill-conceived treaty that allows plaintiffs to go jurisdiction-shopping in _any_ signatory country, even though it has no connection to either plaintiff or defendant, and then have the judgment enforced in _all_ signatory countries, even if it contradicts the national laws of those countries.
Unfortunately, Switzerland is a Lugano Convention signatory, as it Germany. So although Swiss law is clear that Quad9 is in the right, and that was actually just tested and upheld by the Swiss supreme court a couple of years ago, that doesn't matter, because the Lugano Convention takes precedence over national law.
Which is why people tend to get pretty upset about these kinds of treaties. The Trans-Pacific Partnership (TPP) was a similar sort of deal, which the US did _not_ sign, since it was so widely protested.
https://en.wikipedia.org/wiki/Trans-Pacific_Partnership
But, to get back to your specific question, if Quad9 were to just ignore this, Sony would go back to the court in Germany, and get some sort of finding that Quad9 was maliciously failing to comply, it would get damages, and it would request Swiss law enforcement to extract those damages from Quad9. Swiss law would not be able to protect Quad9, and Swiss LE would be obligated to act on Sony's behalf. At that point, Quad9 could only continue to exist by relocating its headquarters to a non-Lugano-Convention signatory country. When we evaluated national legal regimes for privacy protection, Switzerland was best, the Netherlands second-best, and Iceland third-best... All three are Lugano signatories, unfortunately. I'm not sure where we'd wind up, but it would be a huge blow for privacy.
One wonders if Quad9 has its own ulterior motive here, because none of the other DNS providers seem to care, and I find it difficult to believe Sony isn't trying to sue them too.
If anything maybe the reason Sony started with Quad9 is because Quad9 is already a censoring DNS resolver, since by design it censors malware domains, and Sony is saying "well then you should censor copyright infringement too."
Additionally, many DNS resolvers don't turn over records or anonymize. Which doesn't help such companies when they make a claim. These type of companies want the courts to help them to completely destroy the possibility of user privacy or any protection of rights, as it pertains to any claims that they might make. They want to be able to force 3rd parties and DNS resolvers to be compliant to their policies and profits.
Quad9 is special in that it's the only recursive resolver of any size that's not headquartered in the jurisdiction of the Northern District of California federal courts. All three others of the "big four" are, and Quad9 was until it moved to Switzerland so as to be bound by criminal privacy law, and to get out from under USG data-collection requirements.
But Quad9 is _not_ the only one being attacked by Sony. Sony has already won against Cloudflare in other venues, but that's a much easier target.
https://www.musicbusinessworldwide.com/italian-court-orders-...
https://dimitrology.com/cloudflare-wants-to-eliminate-moot-p...
Quad9 doesn't sell hosting services to pirate sites, so has no connection with the alleged infringers. Which is the point of all this. Quad9 is being attacked _because_ it has no relationship with infringing parties. If Sony can establish a precedent that Quad9 can be forced to censor, then that precedent is, in principle, applicable to all parties. Firewall manufacturers. Operating system publishers. Wifi hotspot manufacturers. Open-source software authors. Etc.