There are different levels of security clearance. I had a “confidential” security clearance from the Department of Defense when I worked on airborne radar and flir systems. The next level up was “secret” then above that was “top secret”.
This wikipedia article has a bit more detailed info.
There are different types of security clearances as well. I do industrial control stuff now. One of our customers are the guys who do nuclear fuel processing. Certain areas of their facilities require a Department of Energy Q clearance (DOE clearances are C, L, and Q).
Just because I had a confidential clearance didn’t mean I had access to anything that was marked as confidential. I still had to have a reason for accessing the material. I couldn’t just go browsing through the document vault.
In the U.S. the president is the ultimate authority over classified material. I’m sure there have been incidents where someone in the Dept. of Defense gave the president a bit of a runaround, but technically this is keeping information from the boss. There isn’t some ultimate authority within the DoD that has authority over the president and could keep classified material away from him if they so choose.
The President gets to know whatever he wants to know, whenever he wants to know it. He has the ultimate need-to-know. I’m not sure if there’s an actual read-on process for the dozens and dozens of programs that he has to sit through, which is why my hunch is that once you gain that position, it by default entails access to everything. I’m sure there is a background investigation that’s accomplished at some point on his road to office, so in that aspect he’d be cleared for anything.
There was a link upthread in Post #4 describing the different levels of classification.
I’ve read that Eisenhower enjoyed hearing the details of various spy operations the CIA had going on, but asked not to be told the real names of any of the individuals, as he himself recognized that he had no “need to know” that, and he then couldn’t accidentally or under duress disclose what he didn’t know in the first place.
We had a GQ thread awhile back on whether any Federal employee such as a CIA agent or military officer could keep a national-security-related secret from the President in the face of a direct order to tell the President, and IIRC the consensus was “No,” because the President is the head of the Executive Branch and is ultimately responsible for everything it does. If he wants to know, there’s no legal basis for a subordinate to refuse to tell him. (That doesn’t cover data kept secret under privacy laws, as noted earlier).
We are stuck between a rock and a hard place. We don’t want the government releasing information that puts people, particularly US citizens, in danger, under the ‘location of ships at sea during wartime’ concept. Covert agents, encryption keys, and many other cases fall in that category. That’s the rock, but the hard place is the difficulty in making sure that ‘secrecy’ is not abused. Once the ‘top secret’ stamp is used, it becomes difficult to undo or monitor. If there is a legitimate reason to keep something quiet in the first place, examining it increases the risk of the harm we are trying to avoid, while not examining it increases the risk of abuse.
Notice I used the term ‘we’ instead of ‘the government’. We do have a means of controlling this. We don’t enact and enforce laws individually, we do it through our representatives in a highly defective system that works better than the alternatives. The laws in question can be changed. Safeguards can be added or removed as we desire. We might do better at that if people cared more about our representatives understanding of these issues, instead of their ‘promises’ to give us something for nothing.