The Australian coach had been an interested observer over the past 18 months as NNZ sought to make the shooter a dual international at July's tournament in Singapore.
That quest ended this week when the Switzerland-based organisation refused to consider the issue.
NNZ took its case to the CAS after the International Federation of Netball Associations (IFNA) would not allow Auckland-born Latu to switch allegiance.
IFNA rules stipulate a player cannot represent different nations at successive world championships - Latu played for Samoa in New Zealand four years ago.
NNZ argued IFNA had made an exception when former Silver Ferns defender Vilimaina Davu was able to play for Fiji in 2007, four years after winning gold with New Zealand in Jamaica.
However, IFNA would not grant a clearance and the CAS ruled NNZ had waited too long before appealing to them - the process should have begun when IFNA knocked back NNZ in October 2009, although NNZ chief executive Raelene Castle argued they were still in discussions with IFNA until December last year.
Plummer said IFNA's refusal to budge and the CAS's stance was necessary for the development of the sport.
If Latu had been allowed to play for the Ferns inside the four-year stand down period it would have set a dangerous precedent.
"I guess they (NNZ) had a go but the rules are there for everyone to abide by," she told NZPA.
Plummer said if Latu had been cleared Australia could have approached Jamaican shooters Romelda Aiken and Carla Borrego to play for the Diamonds.
"It would have meant 'Oh well, it's open slather now' and that would be sad because again it's only the strong getting stronger.
"We've already seen the demise of Fiji and South Africa," she said, taking a swipe at NNZ's previous importation of Davu, Irene Van Dyk and Leana de Bruin.
Plummer said NNZ's argument that Davu's exemption to play for Fiji in 2007 backed Latu's case was also flawed.
"It's a totally different scenario to Davu," she said.
"Latu never left New Zealand, she never packed up all her gear and went to live in Samoa. IFNA were also trying to assist Fiji to make them stronger."
In contrast, she said, New Zealand were hardly lacking shooting back-up for van Dyk and Maria Tutaia.
