The ninth online competition for Pokémon Sun and Pokémon Moon has been announced. Weakness Cup will take place from Friday, July 28, 2017 at 00:00 UTC, through Sunday, July 30, 2017, at 23:59 UT. Full details are listed below and on our 7th Generation Online Competitions page which will be updated as new tournaments are announced.

Edit Note: The official site initially announced that this tournament would be Single Battles but later in the day on July 4th, 2017, they changed it to Double Battles.

Original Quote: "Be on guard in the Weakness Cup Online Competition, where every Pokémon in battle is weak to at least five types. Trainers will assemble a team from a limited list of Pokémon, and go head-to-head in Single Battles where an unexpected attack could mean an instant knockout. The battles will take place in Pokémon Sun and Pokémon Moon. Pokémon brought in via Poké Transporter are permitted in battle. All Pokémon will be set to Lv. 50 for the duration of each match."

Weakness Cup

Information
Region: International Registration Period: Thursday, July 20, 2017 at 00:00 UTC, through Thursday, July 27, 2017, at 23:59 UTC Tournament Period: Friday, July 28, 2017 at 00:00 UTC, through Sunday, July 30, 2017, at 23:59 UT Ranking Results Announcement: August 2017 Player divisions: Junior/Senior Division: Born 2002 or later Masters Division: Born 2001 or earlier Junior/Senior Division players are limited to playing between 6 A.M. and 11 P.M., based on the easternmost time zone in each player’s country. Compatible Games: Pokémon Sun and Pokémon Moon Battle Type: Double Battle Banned Pokémon: Eligible Pokémon are restricted to National Pokédex No. 001 through 799 with five or more weaknesses. Mythical and some Legendary Pokémon cannot be used. Entry Gift: Qualified participants will receive Ampharosite, Altarianite, Latiosite, and Latiasite Mega Stones. To qualify, players must complete at least three battles.
Description
Be on guard in the Weakness Cup Online Competition, where every Pokémon in battle is weak to at least five types. Trainers will assemble a team from a limited list of Pokémon, and duke it out in Double Battles. The battles will take place in Pokémon Sun and Pokémon Moon. Pokémon brought in via Poké Transporter are permitted in battle. All Pokémon will be set to Lv. 50 for the duration of each match. The complete list of eligible Pokémon will be available in the competition regulations.
Competition Rules
• Mega Stones are not allowed. • Items are restricted to Weakness Policy and any Berries that lessen the damage taken from supereffective attacks (for example, Babiri Berry, Charti Berry, or Occa Berry). A Trainer’s Battle Team may not have duplicate items. • Register three to six of your Pokémon to your Battle Team. • All Pokémon in this competition will automatically become Lv. 50 for the duration of each match. • A 10-minute time limit for each player will automatically be enforced in-game, beginning at the start of each battle. When a player’s time limit expires, that player will lose the game. • At the beginning of each battle, players have 90 seconds to select three Pokémon with which to battle. • At the beginning of each turn, players have 45 seconds to select a move or change the Pokémon in battle. If a player has not made their selections at the end of this period, the game will automatically make selections for the player. • Players may battle up to 15 games per day of the competition. Any unplayed games will carry over to the following day. A new day begins at 00:00 UTC.

Source: https://3ds.pokemon-gl.com/calendar/#/1/75853b35-c7c4-4d22-ab07-da0c3feb2589