I think there was one scene where one of the forsaken travelled to see Grandal but before they stepped out a small opening appeared first and a chime rang out, effectivly a door bell and Grandal commented on something like someone has remembered their mannors from the AOL.

Personally I's with the idea of ward the area and have teams ready to try to disrupt the gateway forming and if that fails attack the opening but if you are worried how your own people come in there are two solutions. First have designated areas that gateways can open without someone automatically trying to disrupt them This would be a OP version of having one public access door into a high security building.

Option 2 is to employ the door bell gateway to send in a recognition code. Perhaps if its a very secure area combine the two, you can only travel to x room and even then you better have your code sent through before you open a full gateway.