Hi, I have a minecraft server and I would like to block the Code Breaker because some people are stealing to people that doesn't connects to the server.

Thank you.

You can disable it in the server configuration file
either:
Disable allowCodebreakerItem (old versions only)
Or:
Set codebreaker_chance to 0.0 (does not function, still damages durability) or set to -1.0 to effectively make it do nothing.

You can also disable the recipe with a mod like https://kubejs.com/

ok, thank you so much for the information.