The Loving v IRS case makes no mention of "enrolled agents."  The plaintiffs were not EA's.  You can prepare tax returns without being an EA (or CPA, or lawyer).  But if you choose to apply to IRS for EA status, are you agreeing to accept Circular 230 rules, including those that apply to return preparation?

Incidentally, the District Court judge in Loving, whose decision was upheld by the DC Circuit, was James Boasberg, who has been in the news recently.