The union representing port supervisors in British Columbia is formally challenging the legal and constitutional authority of the federal labour minister to order them back to work.

In a legal document dated Tuesday, International Longshore and Warehouse Union Local 514 says it鈥檚 questioning whether the order issued by Labour Minister Steven MacKinnon last week violates the right to collective bargaining and the right to strike.

The union says these rights are protected by the Charter of Rights and Freedoms.

It says the questions will be considered by a panel of the Canada Industrial Relations Board on Dec. 9 and 10.

This isn鈥檛 the only challenge the federal government is facing on this issue, as the union representing port workers in Montreal also announced last week it intended to challenge the federal government.

MacKinnon stepped in on Nov. 12 to get ports in both B.C. and Montreal moving again after employers locked workers out.

His order directed the board to order all operations to resume and move both sets of talks to binding arbitration.