The Assault Vest only prevents the Pokémon from choosing status moves, not from using them. If a Pokémon has selected a status move to use, but obtains an Assault Vest before executing the move, the move can still be executed successfully. A Pokémon holding an Assault Vest can still use status moves via Instruct or Dancer.
Assault Vest was introduced as an Pokémon Tool card in the Pokémon Trading Card Game during the Japanese XY BREAK Era. It was first released in the Japanese Red Flash expansion before debuting in English in the BREAKthrough expansion. When this Pokémon Tool card is attached to a Pokémon, any damage done to that Pokémon by attacks from an opponent's Pokémon that have any Special Energy attached to them is reduced by 40 (after applying Weakness and Resistance).