Arena Trap

Effect:

While this Pokémon is in battle, opposing Pokémon cannot flee or switch out. flying-type Pokémon and Pokémon in the air, e.g. due to levitate or magnet rise, are unaffected. Pokémon with run away can still flee. Pokémon can still switch out with the use of a move or item.

Arena Trap is introduced in Gen 3: