Jefferson's attorneys have filed court papers to appeal a judge's ruling this month that the case against him is valid, The Hill reported Thursday.

The attorneys filed a notice of appeal Wednesday with the 4th Circuit U.S. Court of Appeals, the report said.

Jefferson had urged U.S. District Judge T.S. Ellis III to dismiss the case, arguing that grand jury testimony used against Jefferson violated the Constitution's "speech and debate clause." The constitutional language has been widely interpreted as protecting the legislative work of members of Congress from interference by other branches of government.

Prosecutors argued that interpretation was so overly broad it would preclude any criminal charges against a member of Congress in cases involving crimes associated with congressional duties.

"It's not an expansive immunity," Ellis said in his Feb. 6 ruling. "It's a focused immunity."

Jefferson has pleaded innocent to bribery, racketeering and money-laundering charges. He was indicted in 2007 on 16 counts in connection with alleged bribery schemes involving business ventures in the United States and West Africa.