Pokémon in Box slots unlocked through a membership will appear grayed out once the membership expires, and the following actions cannot be performed on those Pokémon.
• Training
• Changing from trial recruitment to permanent recruitment
• Registration to a battle team
• Participation in battles
• Changes to battle name or title
Even if you return recruited Pokémon to Roster Ranch or send visiting Pokémon back to Pokémon HOME, your locked Pokémon will not be unlocked to fill the newly-created spaces in your Box.
Pokémon that are visiting from Pokémon HOME can still be returned to Pokémon HOME.