Affco's appeal to the Supreme Court, over a long-running battle with the Meat Workers Union in Wairoa, has been dismissed.
The dispute started after negotiations for an expired collective contract broke down.
Affco was the first employer to end bargaining under 2015 amendments to the Employment Relations Act, which allowed firms to opt out of multi-employer agreements and removed the duty, under good faith bargaining, for both sides to reach agreement.
Workers who refused to return to a new season on individual contracts in 2015 were locked out for five months.
The Employment Court ordered the union members return to work, but upon their return they found their terms and conditions were very different.