How to disable the "Take" ticket action for a group?

Hello! I’ve created two privileged users groups (Service Desk Managers and Service Desk Operators).
I’d like the users in the Operators group to not be able to “Take” a ticket, so I disabled the TakeTicket privilege in the “Rights for Staff” tab.
The users of that group, however, still see the Take action if a ticket and are able to use it.
What am I missing?

Thanks!
Alessandro

If you’re on 5.x.x you can use the rights inspector to see why those users are still getting the Take ticket right admin->tools->Rights inspector

Thank you @knation I did it but the TakeTicket permission is assigned only to the Service Desk Managers group (and to root and RT_System of course).
I’m quite puzzled…

If you put that user in the rights inspector and that right, does it say that are getting it from somewhere?

Unfortunately not. I’m thinking it could depend from the long history of our installation (RT3 to 4 to 5…)
I tested what I wanted to achieve on a fresh installation with no data and it worked.