I have never heard of any codified ethical guidelines to using espionage or intelligence sources by historians. They can, arguably, raise ethical questions. For example, I regularly use FBI files from the Cold War. I have quite a tidy collection of the FBI files of many American physicists. Some of these contain flagrant privacy violations of the people involved — tapped telephone conversations, for example, where they gossip about people they like or don't like, things they would never have said in public. These people are all necessarily deceased; the FBI blacks out the names of anyone it thinks might still be alive (though you can sometimes figure out who they are), or anyone who specifically requested they remain confidential indefinitely (but again, you can sometimes make guesses), and FBI files of individuals are closed until the individual's death (you have to provide an obituary in the FOIA request) unless they have given you explicit permission to request the file.

It is a debatable point as to whether the dead have privacy rights. I am not so sure. If they do, then the question becomes, does using these sources validate the original collection of data, or does it re-violate the privacy? Does publishing a privacy violation actually involve a greater privacy violation than the original data collection? (After all, if only the FBI knows what you said, then that is a much more limited sphere than the general public.) I don't know. Philosophers would no doubt have a healthy debate about this. To my knowledge, historians don't — we don't have some kind of line between ethical and unethical sources, all is pretty much treated as fair game.

A much tougher question with FBI files is whether we give them any credence at all. They often contain lots of unattributed smearing. Confidential Informant T-5 says that so-and-so is a communist and a homosexual. Do we report on this? Does reporting on this give this often baseless slander more weight and value that it may have even had at the time? Do we report on it, but then tell the reader that it is probably bunk? (Does this free us from the ethical problem, since we probably reported on it because we know that gossip is titillating?)

A related issue: I wrote a blog post a month or so ago in which I tried to deduce who wrote a rather slanderous letter about Richard Feynman to the FBI. I concluded it was probably his ex-wife, based on circumstantial evidence. I wondered, before publishing on it, whether there were any ethical conundrums here. Is "outing" a Confidential Informant of this sort an ethical problem for a historian? I tried in my post to empathize with her, in particular along the lines that Feynman was no saint and many of her complaints were rooted in different (and arguably valid) interpretations of many things about him which are well known to his biographers. I tried to check if she was still alive or not, and found easy way to tell one way or another (I found a few obits of people with her name, but no confirmation that any of them were her or not) — so I assumed she was not alive (based on her probable age), which maybe is an inappropriate assumption.

I did have a few people e-mail me and ask me whether I thought there were ethical issues involved. I concluded that their might be, but that the historical gain probably offset them, and that anything I was doing now was probably a much smaller ethical problem than the original issues involved. But maybe this is a self-serving conclusion? I don't know. I certainly knew that if I wrote about this that it would be of great public interest (and indeed, the post got about 50,000 views, which is pretty impressive for a history blog!), but whether that weighs for or against disclosure, I don't know (if public interest means increasing the privacy violation, then I guess it would be against).

Ultimately though I tend to err on the side of disclosure. The reason is this: if we allow the intelligence agencies to be the sole arbiters of this kind of information, it sets up a very dangerous precedent. They should not really believe that their actions will be held indefinitely secret, and hiding behind "privacy" (of long since dead people) has become a modern mechanism to not release information by American agencies, often used very inappropriately in my view. So I don't think the answer should be, "the FBI never releases files on people whose privacy it violated, for fear of violating their privacy again." Also I find it highly irritating when the FBI lectures me (in effect) on privacy.

What if we made those files only available to historians, who would then weigh the ethical questions? I think it is problematic for only historians to have access to this information. That is, I don't think it makes it any better to say, "oh, the FBI can know about this, and if I figure it out myself, I get to know about it, but nobody else, because it would be a privacy violation." I either shouldn't get to know about it at all, or I feel I should share it with everyone. Otherwise I risk making myself part of a secret cabal, just an extension of the original power problem. And I can see no justification for that, and it sets up other dangerous precedents (historians who have access to secret sources are also terrible in their own way — they claim an authority they cannot justify, which is not scholarship).

Separately, since I have no clearance or access to anything specifically secret, if I find something interesting in the open archives, I feel like there is very little reason not to write about it, because someday someone else will stumble across it as well. In the Feynman example, I happened to find out afterwards that someone else was writing an article on the exact same letter (which was available on the Internet and easy to find), and made exactly the same identification as I did (they wrote to me afterwards to congratulate me on scooping them). So if this stuff is out there, I figure it is only a matter of time before others find it as well. But this is perhaps an ethical dodge as well.

I doubt you could get all historians to agree on anything about this. The people who use clandestine sources all probably have questions about this lurking in the back of their heads that they happily ignore for the most part, because there are no guidelines or even "best practices," and even if there were, exactly no way to enforce them. This doesn't mean there shouldn't be.

Archivists and librarians are held to a strict ethical code, which notably prescribes they won't disclose confidential information held by law.

I come over secret or private documents when i work a the archives, and there are a lot of things i can't disclose to the public or in my works. Sometimes it's because of a court order withholding publication, copyrights, business agreements, industrial secrets, state secrets, or at other times it's just private archives, etc. 20 years is not a lot, so you there will be some restrictions to data, even for researchers. Not everything is public: there's a line between what's private and public. While this line may be subject to debate, archives around the world have to restrict access regarding the laws of the land and the interest of the public.

If someone would disclose info or publish a work based on confidential informations, the parties involved would have a right to sue, and get a settlement or even the whole destruction of the works.

The situation is similar but different for those of us in ancient Near Eastern studies. The biggest problem we have is the illegal looting of antiquities that eventually find themselves on the black market. Relatedly, we have people like Oded Golan who forge inscriptions and artifacts. Oftentimes, people will rush to publish forged or stolen pieces. Ultimately, we can't at all trust the data that might be gleaned from unprovenanced pieces. Were we to accept or admit such pilfered or forged pieces, the data pool would be tainted in such a fashion that would be entirely detrimental to a field that already occasionally boasts little data as it already is.

Furthermore, there are those who have been caught 'salting' archaeological digs with fakes. This is an expression of the aforementioned problems...