Affco Wairoa is facings claims of thousands of dollars from Meat Workers Union members after the Court of Appeal upheld an Employment Court decision saying they were illegally locked out.
The dispute started in 2013 when a collective contract expired and negotiations broke down after AFFCO wished to change terms and conditions.
Last year workers who refused to return on individual contracts were locked out for five months.
The Employment Court's ordered the workers return in November but upon their return their terms and conditions were changed, such as working night shift when historically they were day shift workers.
After a compliance order was issued they were finally employed according to their collective agreement in February.
The Court of Appeal said ACCO was being anti-union.
"It is obvious that AFFCO's objective was to undermine or compromise the parallel process of negotiating a collective agreement which was then underway with the union," the decision said.
"The company's purpose was to fragment the future bargaining strength of the workforce by isolating individual workers. By this means it took advantage of the inherent inequality of its relationship with the seasonal workers who were members of its captive workforce and to whom it owed existing duties to offer re-employment."
Lockout provisions protected former employees "who have contractual rights to an offer of re-employment".
While the union lockout was illegal, because workers had existing rights from the expired collective contract, the court said the Employment Court was wrong to find AFFCO seasonal work was of indefinite duration and employment was not terminated at the end of the killing season.
In August AFFCO lost in the Employment Court when it asked for the wages owed to locked-out workers instead be calculated as damages.
That would have meant if a locked-out worker took another job until re-employment the worker could only claim lost wages if the other job paid less.
Many union members found alternate employment, meaning they would receive payment for both jobs.