WASHINGTON – An administrative law judge recently rejected a request by McDonald’s Corp. allowing the company to subpoena documents from firms hired by a service employees union as part of a legal battle over higher wages for fast-food workers, the Chicago Tribunereported.

In a ruling earlier this month, Judge Lauren Esposito said that the documents were not relevant. Esposito also said allowing McDonald's lawyers access to the documents— which include the names of current and former employees of McDonald's who are supporting the "Fight for $15" campaign— could have a “chilling effect” on employees.

Fast Food Forward, a group supported by the Service Employees International Union (SEIU), has organized protests at McDonald's and other fast-food locations. The group is advocating a $15 hourly minimum wage and the right for fast-food workers to unionize. Oak Brook, Ill.-based McDonald's announced expanded employee benefits that include wage increases at company-owned stores, paid time off and other benefits.

In the union's case against McDonald’s, the key issue is whether the fast-food company qualifies as a joint employer that can be held jointly liable for labor law and wage violations committed by its franchisees. McDonald’s reported 2,500 independent franchisees in 2014.

The National Labor Relations Board counsel found in July 2014 that McDonald's is a joint employer. If Judge Esposito rules in favor of the union, McDonald's is expected to appeal the decision to the full five-member NLRB panel in Washington.