A production-grade Telegram moderation bot that permanently prevents users who voluntarily leave a protected group or channel from joining it again — unless an administrator explicitly unbans them.
Works for supergroups and channels. Add the bot as admin with Ban Users permission.
Voluntary leavers are added to a per-community blacklist and instantly banned.
If a blacklisted user reappears, they're banned again automatically.
Any admin of a protected community can manage it via /verify_admin.