The Dairy Workers Union is asking the Court of Appeal to consider hearing its case that use of replacement labour by a Waikato dairy company is illegal.
In September the union took Open Country Dairy to the Employment Court, challenging a six-week lockout of its members at the company's Waharoa factory, as well as its use of personnel employed elsewhere while the dispute is on.
While the court found the lockout illegal, it said the company has the right to use the replacement personnel.
The lockout has since been removed, but union members have been unable to return as the company says it is investigating the possibility of environmental sabotage at the factory.
Meanwhile, the union says the parties are continuing mediation over the negotiation of a collective agreement for the workers.