From "Checkboxes vs. Radio Buttons" (J. Nielsen, 2004):
Radio buttons are used when there is a list of two or more options
that are mutually exclusive and the user must select exactly one
choice. In other words, clicking a non-selected radio button will
deselect whatever other button was previously selected in the list.
Checkboxes are used when there are lists of options and the user may
select any number of choices, including zero, one, or several. In
other words, each checkbox is independent of all other checkboxes in
the list, so checking one box doesn't uncheck the others.
In this case:
- you have 2 options: "Access granted" and "Access not granted";
- the 2 options are mutually exclusive.
Therefore, in my opinion, a less ambiguous and more self-evident solution is to use 2 radio buttons instead of a single checkbox:
- As Kara Pernice wrote a couple of months ago: "Radio buttons are tiny in nature, and, thus, according to Fitts’ law, they can be hard to click or tap. To enlarge the target area, let users select an option by clicking or tapping not just that button, but also the label or associated words. This is easier than having to acquire the tiny target of the button itself"
- You will also need to choose carefully the default option. More info about "How to Determine the Best Default Radio-Button Choice" in this article.
- The same goes for the labels ("Not granted" and "granted"), you will need to test them to identify the terms your admins are more comfortable with.