The Globe and Mail reports in its Thursday edition U.S. federal Appeals Court dealt the Justice Department a significant defeat Wednesday, overturning two insider-trading convictions and potentially constraining prosecutors' ability to pursue such crimes. A Wall Street Journal item inside The Globe says a three-judge panel of the Second U.S. Circuit Court of Appeals narrowed the definition of what constitutes insider trading and determined prosecutors had taken too broad a view of the law in their multiyear crackdown on Wall Street. The ruling is a stinging rebuke for the Manhattan U.S. Attorney's Office, headed by Preet Bharara, which had a near-perfect record in insider-trading cases. The ruling means the convictions of Todd Newman and Anthony Chiasson are overturned. Prosecutors are likely barred from retrying Mr. Newman and Mr. Chiasson because the court dismissed their indictments with prejudice. The Manhattan U.S. Attorney's Office had planned to retry the cases, according to people familiar with the matter. "The decision affects only a subset of our recent cases," said Mr. Bharara. There now could be grounds to overturn the marquee conviction in the SAC Capital Advisors case.