Nintendo obviously doesn't think they have standing against emulators [0]. However they they can make the lives of defendants hell until the emulator devs settle.

Now, I think there are laws to curb this kind of judicial abuse, called anti-SLAPP laws. But reading about it, it seems to apply to defamation lawsuits. Apparently it's okay to threaten legal action in bad faith when it's, say, regarding non-existent copyright infringement.

https://en.wikipedia.org/wiki/Strategic_lawsuit_against_publ...

[0] to be fair, they might get something out of the anti-circumvention clause of DMCA. But this only applies if devs aren't careful enough (or don't know about this technicality). Developing an emulator to run legally acquired games doesn't break any laws.