Bug_FieldChange = False
On Error Resume Next
If User.IsInGroup("Developer") And Bug_Fields("BG_STATUS").value= "Closed" then
Msgbox "You do not have permission to perform this action"
Bug_FieldChange = True
On Error GoTo 0
there is an alternate way instead of workflow to acheive this.
go to Tools >Customize>Groups options
and next to the group click on group you want to change the persmissions and on the left hand side there is an option change click on that button - select the tab for which you want to change persmissions and can change .( check or uncheck the permissions in that module) and then save.
Note: You can not change the system groups here, but you can create a new group and add the users to this group and modify the permissions from here.