The Trump administration escalated its effort to punish a sitting U.S. senator for protected political speech Monday, formally converting the Pentagon’s review of Sen. Mark Kelly (D-Ariz.) into an official Command Investigation under military law.

The escalation marks a significant shift. While the administration has not filed charges against Kelly, the act of placing a sitting senator under a Command Investigation for speech critical of the president represents a dangerous departure from democratic norms.

A Command Investigation is a formal military fact-finding process ordered by a senior commander to determine whether misconduct occurred and what, if any, action should follow. Unlike the Pentagon’s earlier preliminary review — which was largely an internal legal assessment — a Command Investigation authorizes an investigating officer to gather evidence, conduct interviews under oath and produce official findings and recommendations.

The Pentagon confirmed the move in a statement provided to reporters.

“The Office of the Secretary of War, in conjunction with the Department of War’s Office of the General Counsel, is escalating the preliminary review of Captain Mark Kelly, USN (Ret.), to an official Command Investigation,” a Pentagon official said. “Retired Captain Kelly is currently under investigation for serious allegations of misconduct. Further official comments will be limited to preserve the integrity of the proceedings.”