I would encourage checking with the Immigration Court, but I believe that it is like Social Security Court where anyone licensed in an ABA Jurisdiction can practice in their courts just by filing an appearence.
Do check though, since Tax Court I know for example requires that you file some paperwork (super easy but still required first) and it may be like that.
I doubt that it is as complicated as say Patent Court which has its own exam and other barriers.
I have not practiced in it myself but did see it advertised on Docketly awhile back for an Attorney seeking an Appearance Attorney with no reference to any specific additional license required (take that for whatever it is worth).
The following link is to an Avvo discussion on the same topic, it may help. Avvo is answered by lawyers, but lawyers (especially the ones with decades of experience) are OFTEN WRONG (laws change) plus a lot of people comment on it just to get their "rating" up (based in part on number of replies) which is why you see so many nonsense answers and total waste of time stuff like "ask a lawyer". It can be.....painfully stupid......take with grain of salt (if not the full saltshaker) is my point. But link below all the same to it. https://www.avvo.com/legal-answers/...20073.html