I have no special insight into power politics between the executive and legislative branches of government, but I do seem to recall that it was the chairmen of both the House and Senate intelligence committees (Sen. Bob Graham, a Democrat, and Rep. Porter Goss, a Republican) who asked the Justice Department to conduct a leak investigation, pledging their full cooperation.

I don't recall any members of the intelligence committees having publicly raised any "separation of powers" objections to this investigation until they were asked if they would submit to polygraph "tests."

I don't see how the FBI leak investigation (asked for by Congress) would have a chilling effect on Congressional oversight regarding Sibel Edmonds' allegations, especially as those who have raised the issue of Edmonds' claims with the Attorney General (Senators Leahy and Grassley) are on the Judiciary Committee and not the Intelligence Committee.