The exception for interoperability only applies to _the minimum required_ for interoperability. You can use this exception to distribute e.g. game authorization code even if copyright would not allow you to do it.
You _cannot_ use this as an excuse to pirate the entire program, much less to create your own derivative work and distribute it!
This is just wishful thinking that comes up every so often in these threads (now it is the 5th time I see this parroted here). And then, when Nintendo inevitably shuts everything down, cue the crying. This ignorance is simply setting these projects for failure.
And Nintendo can pound sand, sorry. The only realistic ways to play those aging games is on an emulator or recompilation projects nowadays.
Nintendo also didn't strike these projects, maybe they are afraid of making a precedent.
There is a bazillion of jurisprudence about decompilation in the EU . Just search for your favorite case. I'm based in the EU (France). But FYI, despite what you may think, in practice the US is more lax about this than the EU is.
In the EU, for example, decompilation even if you don't distribute may very well be illegal (because it would be an unauthorized temporary copy of the program); the US courts are way more lax when it comes to these temporary never-distributed copies (which are almost always fair use, a concept that doesn't exist per-se in the EU). This is a big problem in the EU for security research (which obviously does not fall into interoperability).
Emulation would be acceptable, which is yet another reason the interoperability clause does not apply (since you _already_ have a way to interoperate that doesn't require distributing copyrighted software, and the EU interoperability clause very explicitly says that then it does _not_ apply).