Actually, it could tie into the First Amendment. They point out that it's a journalism issue. This would be closely related to issues that journalists deal with when protecting sources. While that doesn't always work, the idea is that the press needs a certain amount of latitude in being able to protect their sources or have access to material that, for various reasons, may not be printable without consequences.
But, since the internet is an international object, something else comes into play here. In college I had a chance to meet and talk with Howard Morland, who was, at the time, semi-famous for having (inaccurately, it turned out later) figured out the linking mechanism between how an atom bomb triggered a hydrogen bomb. He had travelled around the country, doing different interviews and talking with people to figure out more about this. At the time, of course, it was all top secret. He wrote an article for a magazine called "The Progressive." Unwisely, the editors at "The Progressive" sent the article into the DoE for verification. All sorts of men in black with guns showed up and there was a huge court case. The design, which had been worked out from completely non-classified material, was given a classified status and was censored.
There was, however, one copy of the paper that had not been confiscated by the government and was with someone who, at the time, was travelling internationally. This person got it to a publication that was able to print it in their country. Once that information was published and openly available, even if it wasn't in the U.S. (and I think copies were sent into the U.S.), it became public knowledge and was no longer classified. (For details, read "The Secret that Exploded," by Howard Morland.)
So Sony may try going after Americans with that information, but once the documents become published and public knowledge, they can't really do too much about it.