The Special Battle rules for Season 3 of Pokémon Sun and Moon have been revealed. Season 3 will run from March 21 to May 15 and requires all Pokémon to be holding Z-Crystals. The base rules for this season are as follows:
Battle type: Single Battle
Pokémon Restrictions: National Pokédex.
Banned Pokémon: Mewtwo, 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, Zygarde, Diancie, Hoopa, Volcanion, Cosmog, Cosmoem, Solgaleo, Lunala, Necrozma, Magearna, Ash-Greninja
Item Restrictions: All Pokémon have to hold Z-Crystals
The other standard rules apply, including all set to Level 50 if above that, and you choose 3 Pokémon out of your 6, and you cannot have two Pokémon holding the same hold item.