SPRINGFIELD — Illinois lawmakers are free to pursue their own investigation into House Speaker Michael J. Madigan’s role in a bribery scheme involving utility giant Commonwealth Edison, as long as they don’t specifically ask witnesses what information they’ve shared with federal investigators or a federal grand jury.That was the word late Thursday from John R. Lausch Jr., the U.S. Attorney for the Northern District of Illinois.“We recognize the (Special Investigating Committee’s) separate and independent responsibilities …