The U.S. Securities and Exchange Commission’s attempt to claw back more than $4 million in compensation from the former chief executive officer of an Arizona automobile parts retailer raises “constitutional questions of the gravest magnitude,” the defense argues in a motion to dismiss filed on Tuesday.

On July 22, the SEC brought suit against Maynard L. Jenkins, 67, former chief executive officer of the defunct CSK Auto Corp., seeking reimbursement on behalf of shareholders under the Sarbanes-Oxley Act. Jenkins, who had signed many of the company’s financial documents, earned more than $4 million in bonuses and stock sales for a period during which CSK twice was forced to restate its accounting due to alleged misconduct related to vendor allowances.