If you have allowed a user delegate control permissions. For example, for the user to be able to modify groups but you now wish to remove the control, follow the instructions below:

1) Open Active Directory Users and Computers
2) Click View
3) Enable Advanced Features (If already enabled, you should see a tick)
4) Right click on the folder you set delegate control on
5) Click properties
6) Click the security tab
7) Remove the user/group
8.) Click ok