Constitutional issue in the news: In the case of the FBI and Congressman Jefferson the court held that investigators violated the Constitution by reviewing legislative documents as part of a corruption investigation.

What the three-judge panel of the U.S. Court of Appeals for the District of Columbia Circuit is referring to in their decision is that the Constitution grants some immunity for members of Congress.

They shall in all Cases, except Treason, Felony and Breach of the Peace, be privileged from Arrest during their Attendance at the Session of their respective Houses, and in going to and returning from the same; and for any Speech or Debate in either House, they shall not be questioned in any other Place. (US Constitution Article I, Section 6, Clause 1)

The Supreme Court has held that the application of this immunity is limited to the application to activities that are "clearly a part of the legislative process." (United States v. Brewster 1972) This protection, as long as "legislative process" test is met, is considered absolute. Yet if the action does not meet the test they are just as subject to criminal prosecution as anyone else.

So in the case of Congressman Jefferson the court is addressing the FBI's examination of materials directly linked to the legislative process. The court did not rule against the examination of any other materials found in their search of Jefferson's possession.