Lobby group Save TVNZ7 has hired high-profile constitutional lawyer Mai Chen to examine whether the Government has acted lawfully in its decision to axe funding for the free-to-air channel.
New Zealand's only commercial-free, public service television station will close this month after the Government decided not to extend its $79 million funding over six years, $70m of which came from a special dividend from Television New Zealand.
TVNZ7 will become a TV One Plus One channel.
Save TVNZ7 spokesman Myles Thomas said Ms Chen would consider whether Save TVNZ7 could seek a judicial review of the Government's decision.
She would also look at whether TVNZ was "complicit" in its agreement to follow the Government's recommendation to close the channel.
It was vital that public service television was retained because without it New Zealand was left with only commercial broadcasters.
"That means our news is prey to commercial interests and everything is simplified because commercial programmes don't want anyone to change channel.
"It affects how they approach the news. Everything is reduced to simplified messages and soundbites.
"There is no analysis."
Ms Chen would determine by the end of the month whether she would take legal action on behalf of Save TVNZ7, said Mr Thomas, a television director.
About 31,000 people had signed Save TVNZ7's online petition and donations to the lobby group had enabled it to hire Ms Chen.
"It's an expensive business going down this path but we are determined to keep public service television in New Zealand."
Labour's broadcasting spokeswoman, Clare Curran, said public broadcasting was crucial for New Zealand's culture and heritage.
"The Government doesn't seem to understand there are many thousands of New Zealanders who believe public broadcasting is a right of citizenship."
There were important points of principle to test over the Government's decision not to continue funding the channel, she said.
Broadcasting Minister Craig Foss said TVNZ7 was set up with time-limited funding in 2006 to encourage people to "go digital" ahead of the digital switchover.
"The Government values Kiwi content and invests $230m each year on public broadcasting and supporting New Zealand content on our screens."
Recent audience data shows TVNZ7's audience has grown from 863,100 last year to 1.47 million, comparable with the audience of Maori Television.