The Court of Appeal upheld an Employment Court decision that the lockout was unlawful, saying it was "obvious that Affco's objective was to undermine or compromise the parallel process of negotiating a collective agreement which was then under way with the union.
Affco was the first employer to end bargaining under 2015 amendments to the ERA, which let firms opt out of multi-employer agreements and removed the duty, under good-faith bargaining, for both sides to reach agreement.
The Wairoa dispute started in 2013 when a collective contract expired and negotiations broke down after Affco wished to change terms and conditions.
In 2015 Wairoa workers who refused to return on individual contracts were locked out for five months.
The Employment Court ordered the union members' return to work, but on their return their terms and conditions were changed markedly.
After a compliance notice was issued they were employed according to their collective agreement.
Jagose said the nature of the work meant employment contracts with seasonal workers were regularly being terminated and picked up again, and during the time the contract was terminated they were not in an "employment relationship".
Justice Arnold asked whether this meant certain benefits that could be given to long-serving employees were not given to seasonal workers, such as extra holiday leave for longer-serving workers.
Jagose said this was the case.
Justice Arnold said it seemed to be a "pretty hard position" for employees that had accrued rights or the opportunity to access particular benefits.
He questioned whether the purpose of the structure was "to remove a number of those benefits".
Jagose said that was what happened when employment was terminated for seasonal workers, even if they were to be employed again next year.
"Your honour's point is that it is rough. Well, yes it is. But that's the contract."
He said the workers lost their entitlement to continuity of service.
Justice Arnold said the attitude failed to "grapple with the fundamental nature of this agreement".
"You say, well, it's a whole series of employment termination, employment termination, employment termination sequences that occur, and yet the agreement provides a range of benefits that are treated as though it's a long service of employment, a long period, a continuous period of employment ... on this particular termination and re-employment, the employer is free to disregard the benefits that have accrued to the employees."
"It seems to me this contract offers a broad range of benefits reflecting continuing service. You have asserted a position that you can do away with the whole lot."
This was not caught under the legislative provisions for lockouts, Justice Arnold said.
Jagose said in this situation, the collective agreement had expired for those workers.
The case continues.