WASHINGTON (AP) — The FBI violated the Constitution when agents raided U.S. Rep. William Jefferson’s office last year and viewed legislative documents, a federal appeals court ruled Friday.

The court ordered the Justice Department to return any privileged documents it seized from the Louisiana Democrat’s office on Capitol Hill. The court did not order the return of all the documents seized in the raid.

Jefferson argued that the raid trampled on congressional independence. The Justice Department said declaring the search unconstitutional would essentially prohibit the FBI from ever looking at a lawmaker’s documents.

The U.S. Court of Appeals for the District of Columbia Circuit sided with Jefferson on the constitutional issue.

‘‘The review of the Congressman’s paper files when the search was executed exposed legislative material to the Executive,’’ and violated the Constitution, the court wrote. ‘‘The Congressman is entitled to the return of documents that the court determines to be privileged.’’

The raid was part of a 16-month international bribery investigation of Jefferson, who allegedly accepted $100,000 from a telecommunications businessman, $90,000 of which was later recovered in a freezer in the congressman’s Louisiana home.

Jefferson pleaded not guilty in June to charges of soliciting more than $500,000 in bribes while using his office to broker business deals in Africa. The Justice Department said it built that case without using the disputed documents from the raid.