The legality of the emulation itself has long been established, but I've been concerned for a while that illegal DRM circumvention of the games themselves has been a viable legal avenue. Under the DMCA, even the process to dump your own legally-licensed games has arguably been in a legal grey area for a while now, with how they are locked down. If any method to playing the games become illegal, any unauthorized emulation of games becomes de facto illegal.

I'd cite legal precedent here, but there's been a substantial right-wing, pro-corporate shift in American courts over time. Who knows how this will go.