How to Unban Without Console or In-Game?

[wtitus]

How do I do this?

[Caustic Soda-Senpai]

Use the RCON, it makes life easier. If you don't have access to it, contact your server owner.

[JamminR]

Not a ULX question, but leaving it here, for now, anyway.
Shut down server. MUST shut down.
Add offending players steam ID to /cfg/banned_user.cfg
Start server.
If ULX is installed, person is banned.
If not, hope one of your scripts runs "exec banned_user.cfg" from console on server startup.