We nat dex with blue pentagon now.
"Players may use Pokémon from the National Pokédex, from No. 001–719, that are caught in the game, transferred from a previous Pokémon title, or received at an official event or distribution
The following Pokémon may not be on a player’s team:
150 – Mewtwo
151 – Mew
249 – Lugia
250 – Ho-Oh
251 – Celebi
382 – Kyogre
383 – Groudon
384 – Rayquaza
385 – Jirachi
386 – Deoxys
483 – Dialga
484 – Palkia
487 – Giratina
489 – Phione
490 – Manaphy
491 – Darkrai
492 – Shaymin
493 – Arceus
494 – Victini
643 – Reshiram
644 – Zekrom
646 – Kyurem
647 – Keldeo
648 – Meloetta
649 – Genesect
716 – Xerneas
717 – Yveltal
718 – Zygarde
719 – Diancie
Pokémon must be placed in the Battle Box
Pokémon are allowed to Mega Evolve.
Pokémon may not hold the item Soul Dew.
Pokémon above Level 50 are permitted, but they are auto-leveled down to 50 for the duration of battle.
Players may use Pokémon with Hidden Abilities.
Players may use items that have been officially released via Pokémon X, Pokémon Y, Pokémon Omega Ruby, Pokémon Alpha Sapphire, the Pokémon Global Link, or an official event or promotion.
In addition to the requirements outlined in section 10.1, Pokémon used in the Standard format must have a blue pentagon in the Pokémon summary screen. This indicates that the Pokémon was caught during regular gameplay, hatched from an Egg, obtained within the game, or was officially gifted in either Pokémon X, Pokémon Y, Pokémon Omega Ruby, or Pokémon Alpha Sapphire."
source:
http://nuggetbridge.com/forums/topic/11082-2015-vgc-rules-published/#entry153529 