denileigh,
I suggest that you verify who the current user is for my suggestion should work. Add this to the OnOpen event of the form...
MsgBox "Current User = " & CurrentUser
Also, removing the permissions as suggested above should work but that will prevent you from customizing a message to alert the user that they are not allowed to open that form.
You have to take an extra step since you are using a custom menu bar or tool bar. If you were using a custom navigation "main menu" form that displayed the command buttons to open each form in the db then you could set the visible property to "No" if the current user = "Admins" for a specific command button. That way the Admins users would never see the button to open a form that they are not allowed to open.
HTH