Pokémon Ultra Sun and Pokémon Ultra Moon have been updated to version 1.2. The moves Curse, Forest's Curse, Power Trick, and String Shot are no longer banned from Play! Pokémon video game tournaments. The new update is required to play in tournaments. To update your game, visit the Pokémon Ultra Sun or Pokémon Ultra Moon entry on Nintendo eShop and then download the latest patch.
The full rules can be found on the Play! Pokémon Rules & Resources page.