The precedent that almost everyone cites (because it is some of the only) is Sony vs Bleem.
https://en.wikipedia.org/wiki/Bleem!#Sony_lawsuit
Initial release was in 1999 and lawsuits were around the same time. PS2 launched in 2000. So while the bleem marketing was a complete mess, the emulator existing while a console was still "alive" does not matter in the slightest.