Using FLAN as claim management system, the Chisels do not respect claimed areas and anyone can start chipping away someone else's blocks.

You can use their api

edit: I'm pointing this out to the chisel's dev, not the issue's OP btw

Bits can still be placed in claimed areas after the last commit, both on new blocks and inside of existing chiseled blocks. It looks like the check is done on the client rather than the server.

This issue is still happening on latest 1.18.2 version of the Mod, and it doesn't seems to have been fixed on 1.19 either by looking at the changelogs...