Comment 2 for bug 1394069

another type of block was added - to block all commands that change current environment.

To sum up:

destroy-environment includes command:
    destroy-environment

remove-object includes termination commands:
    destroy-environment
    remove-machine
    remove-relation
    remove-service
    remove-unit

all-changes includes all alteration commands
    add-machine
    add-relation
    add-unit
    authorised-keys add
    authorised-keys delete
    authorised-keys import
    deploy
    destroy-environment
    expose
    remove-machine
    remove-relation
    remove-service
    remove-unit
    resolved
    retry-provisioning
    run
    set
    set-constraints
    set-env
    unexpose
    unset
    unset-env
    upgrade-charm
    upgrade-juju
    user add
    user change-password
    user disable
    user enable

For more information, please run

juju help block
juju help unblock