Blocking the "Disable filter" dosn´t work

[Buggy-c]

I want to block the Menuitem "Disable filter".
Our users should be allowed to disable the filter for one side, but not complete.

Hiding the menueitem dosen´t work.
Using the prefernces should work, but didn´t prevent from disabling the filter.
I set in the mozilla.cfg the line >lockPref("extensions.adblockplus.enabled", true);<
Checking it with >about:config< shows the line in italic, so it is locked. But i can still toggle the filter on and off as i want.
Without the lockPref this line ist changing with the menue.

How can i fix the filter to stay on.

We are using Win 7 and the FF 24 esr.

[greiner]

Setting the value of "extensions.adblockplus.enabled" to "true" only means that adblocking is enabled but not that any filter is active (see en/preferences).

Locking filterlists and/or filters to keep them enabled is currently not possible. May I ask for the reasons for that requirement?