A federal appeals court on Monday denied the request of former Rep. Rick Renzi (R-Ariz.) to rehear arguments as to whether the corruption case against him can proceed, potentially setting up a Supreme Court showdown over the application of a constitutional clause that has become a legal shield favored by wayward lawmakers.

Renzi’s team had asked the 9th U.S. Circuit Court of Appeals — which hears appeals from lower federal courts in Alaska, Arizona, California, Hawaii, Idaho, Montana, Nevada, Oregon, Washington and Guam — for a rehearing before the full court last month after a three-judge panel ruled in June that the Justice Department’s prosecution of Renzi on corruption, extortion and fraud charges could proceed.

The judges had rejected Renzi’s argument that the Constitution’s Speech or Debate Clause shielded him from prosecution because it was designed to protect legislators from investigation and prosecution by the executive branch over actions undertaken as part of their official duties. His attorneys requested to reargue the case before the full court. The court denied the petition in a one-page order Monday.

Legal experts told Roll Call that the court’s strongly worded ruling in the case — and the fact that it conflicted with the outcome of similar cases in other appellate courts — all but set the stage for the case to go to the Supreme Court if Renzi’s lawyers appeal.

His attorneys had in part relied on a ruling in a case before the U.S. Court of Appeals for the D.C. Circuit that arose from the investigation of former Rep. William Jefferson (D-La.), who is now infamous for stashing thousands of dollars in his freezer. The judges in that case interpreted the Speech or Debate Clause more broadly than the three-judge panel that heard the Renzi case in the 9th Circuit.

“Simply stated, we cannot agree with our esteemed colleagues on the D.C. Circuit. We disagree with both [the case’s] premise and its effect and thus decline to adopt its rationale,” Judge Richard Tallman wrote on behalf of the 9th Circuit panel.

Melanie Sloan, executive director of the watchdog group Citizens for Responsibility and Ethics in Washington, said at the time of the opinion that it could take the case to the nation’s high court.

“Given that the court explicitly declined to follow the D.C. Circuit’s decision … it appears the question of how broadly to interpret the clause may be headed to the Supreme Court,” she said.