illegal.
Just a small nitpick--EULAs are written by corporate lawyers, not legislators.
This is for all of you. Please be more careful about tossing the word
illegal around. It's a severely loaded word that's capable of causing anxiety, in this case where it's undue. If you're going to use that word, you should be able to quote federal laws alongside it. The reason no one ever does this is because there aren't any federal laws on the matter to quote. When you see people like me say (over and
over and
over) that all of this exists in a legal gray area, we're not mincing words or obfuscating some actual law somewhere. It exists in a legal gray area because servers and clients and emulators turn into a logical mess of spaghetti in the few cases when they do make it into the courts. This is scary for publishers, because there is a risk that at some point, precedence will be set against their favor at a high level in the courts.
Regardless, the legal process is enormously expensive for the rest of us, and server emulators almost always buckle at the sight of a cease and desist take-down notice. Those are written by corporate lawyers too, by the way, and can say just about anything those lawyers dream up--because they're not restricted by legal or even ethical standards. This is why people sometimes call them legal bullies. That's quite literally what some publishers pay them to be.
Finally, bear in mind that if emulators were literally illegal, publishers would risk nothing by taking all of the emulator creators to court. Companies like EA would not be able to give even limited blessings to fan-based server emulation projects like RunUO and Earth and Beyond Emu, because doing so would mean breaking the law. We would all be living in an alternate reality. Because that's not what happened in our universe.
At this point, armed with new knowledge, you may be asking yourself why you ever used the word illegal in the first place. Well, you probably did it because you heard someone else do it, or because you took the EULA and TOS for a video game as a legal document. Neither will lead to an accurate summary of the legal status of an emulator. Corporations deem EULAs as legally binding contracts, but some of the things publishers have asked players to sign over aren't even allowable in some states and countries; and the nature of a EULA's presentation and "signing" method has also been challenged by some of the same digital rights activists who labor to keep the World Wide Web open and free from government and corporate censorship and regulation--you know, the people who ask you to sign a petition every year or so and who've asked website owners to make their sites go dark for a day.
This issue goes beyond video games, and when you support the idea that software reverse engineering and server emulators are "illegal", you are supporting a whole range of nasty, greedy ideas espoused by the kinds of people who are seeking a wide scope of "ownership" over things that legal philosophers have generally agreed should not be ownable. If you knew what side you were putting yourself on by using the word illegal in this context, you'd probably not be happy with yourself. At all.
TL;DR: If you'd like to groupthink something, groupthink the idea that a non-profit, fan-based server emulation project isn't illegal.