First of all the source for this is in Nahar Shalom pg. 34 (140 new edition) by Rabbi Shalom Shaarbi. Also, just want to remind people that I don't want to get into Kabbala here which I always remind people is Asur (see Shut HaRashba 1:414, Yabia Omer 10:23, Yechawe Daat 4:47, Rama Y"D 246:6, Or LeSion Helek HaTorah, ch. 7 and more). The reason is because the word Kabala means "receive" or "accept". Therefore, everything that is learned has to be from Eliyahu HaNavi. Halacha is something we call "Lo Bashmayhim Hi- not in Heaven" meaning it has nothing do with what the Metziut (fact) is, it is based on Rov - majority or according to some logic. Kabbala is not like that, Kabbala from the Ari is called by the Rashash "Divre Elokim Hayim- words of G-d that are alive" (see Eruvin 13b) meaning that they are literally the Metziut. Therefor we must only accept the Arizal because he was appointed by Hashem to transmit Kabala through R' Haim Vital. As I said before, it isn't like Halacha where the decisions are made down here (Lo BaShamyim Hi), but it is "Divre Elokim Hayim- words of G-d."
Please tell me if you need more than this, and precisely what you need.
EDIT: I forgot to mention, this applies to ALL other Kabalists as well (including Shaare Ora, Chassidus, and all others that don't follow the exact path of R' Haim Vital, Rashash, and Ben Ish Hai.