This time around, Nintendo is arguing that by using prod.keys, Yuzu is a copyright protection circumvention product in violation of 17 USC §1201 (a)(2).

No person shall manufacture, import, offer to the public, provide, or otherwise traffic in any technology, product, service, device, component, or part thereof, that—

(A) is primarily designed or produced for the purpose of circumventing a technological measure that effectively controls access to a work protected under this title;

(B) has only limited commercially significant purpose or use other than to circumvent a technological measure that effectively controls access to a work protected under this title; or

(C) is marketed by that person or another acting in concert with that person with that person’s knowledge for use in circumventing a technological measure that effectively controls access to a work protected under this title.

The reverse engineering protection under the DMCA only applies to 17 USC §1201 (a)(1)(A), so there's a very real and very scary possibility of Nintendo winning this one and setting a precedent if they can convince a judge that Yuzu's is primarily for DRM circumvention.

That‘s the thing with huge, shitty corporations. Even when they know they‘re absolutely in the wrong, they can still go after the small fishes and make their lives hell.

To give another example, LEGO has been flooding small toy sellers in Germany with cease and desist letters for selling sets from competitors that might look like knock-offs to some, but are perfectly legal because LEGO does not own the brick system. And of course they would never go after Amazon for doing the exact same. Only small sellers that are ruined if they can‘t scrape the money together for a proper legal defense.

Just being an expensive pain to the developer dissuades future developers.

Nintendo has lost this type of case before. Their strategy is usually to drain the defendant of cash.