The Rhinos are demanding a A$400,000 transfer fee for the former Penrith hooker after he walked out on them with two years left on his contract.
Segeyaro's manager Sam Ayoub has told News Corp that the contract was not valid amid rumours the former Penrith hooker is close to agreeing to a move to NRL champions Cronulla for 2017.
However, Hetherington told Press Association Sport: "We have a bona fide contract that is currently lodged with the RFL. If they want to go through the courts, that's their prerogative."
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Hetherington says Segeyaro signed a two-and-a-half year deal when he joined the club from the Panthers last June, with a get-out clause to opt out on or before September 30, a deadline which passed with the player apparently happy to stay.
Segeyaro was an instant hit with the 2015 Super League champions, helping them to nine wins from their last 10 matches of the season.
But he underwent a change of heart while back in Sydney and failed to report for pre-season training earlier this month.
Leeds signed a replacement in ex-Manly rake Matt Parcell and slapped a transfer fee on Segeyaro.
"He terminated that contract by failing to return to the club but he remains on our register and on the transfer list," Hetherington said.
"We have had no request from Cronulla and the NRL have confirmed that while ever he is registered with the RFL he cannot be registered with them."
