What made Gisborne Milk unusual for Fonterra was that the company processed milk for its local community, shipping excess supply to the Bay Milk operation without producing its own product.
The distance and nature of Gisborne Milk's shareholding was seen as a problem for Fonterra, though the dairy group didn't devise a way to deal with the issue for several years, even with prodding by its supplier.
Justice Ellis said Fonterra's interpretation of the act that Gisborne Milk couldn't be a shareholder was incorrect, but the dairy group was entitled to put it forward as an honestly held and reasonable opinion.
Gisborne Milk wasn't obligated to sell its shares, and in doing so ignored legal advice it had received that Fonterra's position was wrong, the judgment said.
"The evidence from Gisborne Milk's own witnesses leads to the conclusion that a decision was taken by Gisborne Milk to voluntarily surrender its shares, for a number of perfectly sound reasons," the judgment said.
The judgment doesn't determine a separate action by Gisborne Milk shareholder Opoiti, which claims a letter from Fonterra manager Mark Leslie caused it to enter into an individual contract with the dairy group.