Details: Like all Battle Facilities, there are given rules to The Battle Tree. All battling modes have the standard flat rules that prevent two of the same Pokemon species and items attached to such. There are also a list of Banned Pokemon that are prevented from being used, mainly Legendary and Mythical Pokemon. Not all Legendary Pokemon, however, are banned, such a the Island Guardians and Ultra Beasts.
Banned Pokemon of The Battle Tree:
Mewtwo
Mew
Lugia
Ho-Oh
Celebi
Kyogre
Groudon
Rayquaza
Jirachi
Deoxys
Dialga
Palkia
Giratina
Phione
Manaphy
Darkrai
Shaymin
Arceus
Victini
Reshiram
Zekrom
Kyurem
Keldeo
Meloetta
Genesect
Xerneas
Yveltal
Diancie
Hoopa
Volcanion
Cosmoem
Solgaleo
Magearna
Marshadow