What government official holds the highest security clearance?

Answer 1

There is no such thing as the "highest security clearance". Basical clearances that applyt across the board are "Classified", "Secret" and "Top Secret". However, "over" that are compartmentalized clearances. A compartmentalized clearnace may mean that you're cleared to know about and even enter a facility, but you aren't cleared to open all the doors, or know what's going on in every one -- those would rquire seperate, compartmentalized clearances. The idea is that, keeping all your secrets in one place always causes trouble. Such a place or a person would be a target. And in the event of them wanted to do something as simple as taking a vacation, some projects may come to a halt. Instead, over TS rating, security is compartmentalized. As dramatic example would be that, if the President of the United Stated of America, walked up to the gate at San Onofre Nuclear Power Generating Station one evening, and demanded entrance, he'd be turned away. That said, the President of the US, aka "National Command Authority" probably holds the highest overall set of clearances, with various members of the JCoS coming in a close second. But even they operate on a "Needs to know" basis.