This is due to a handshake agreement made a few years ago with an NRL club
All Black centre Sonny Bill Williams announced Monday he will quit the World Cup champion New Zealand team to play in Japan, then return to his old stomping ground, Australian Rugby League.
Hailed as a "freakish" athlete by national coach Steve Hansen, the 26-year-old called time on a brief but eventful 17-Test Rugby Union career, which included helping New Zealand to victory at last year's Rugby World Cup.
Williams said he had signed with Japanese side Panasonic, in a deal reportedly worth NZ$1.4 million, and would then switch to an unspecified National Rugby League (NRL) team in Australia.
"This is due to a handshake agreement made a few years ago with an NRL club," he told reporters.
"I am not in a position to elaborate on that."
Williams, who also juggles a career as a part-time boxer, is widely tipped to join Bondi-based glamour club the Sydney Roosters.
He made his name in the NRL, winning the 2004 premiership with the Canterbury Bulldogs in his rookie season before controversially walking out on the club four years later and switching to Rugby Union with Toulon.
In 2010, he turned down a world-record NZ$5.0 million offer from the French club and joined the Crusaders in the Super Rugby competition, intent on breaking into the All Blacks World Cup squad.
The 1.91 metre (6ft 3in), 110 kilogram (17.3 stone) centre impressed enough to earn his All Black debut against England in November 2010, even though he was a Rugby Union novice with only a handful of senior games in New Zealand.
Hansen said that, at the time, Williams had limited understanding of the 15-a-side game but made up for it with his freakish abilities and high skill levels.
He said Williams had since developed his rugby smarts to become a truly world class player, citing his performances in the recent series whitewash against Ireland.
"While Sonny has been with New Zealand rugby for only a short time, his contribution has been immense," Hansen said in a statement, adding that he was disappointed at Williams' departure but wished him well.
Williams' management ensured the player signed only one-year contracts after he returned to New Zealand, leaving his options open after the World Cup.
After a year with the Crusaders, when the Christchurch team made the Super Rugby Final, he moved to the Chiefs, who currently lead the competition and are favourites to win their first title.
That would allow Williams to leave New Zealand rugby on a high. He will not participate in the Rugby Championship, the revamped southern hemisphere competition featuring New Zealand, South Africa, Australia and Argentina.
Williams, who is also the New Zealand heavyweight boxing champion with a career record of five wins, three by knockout, did not rule out the possibility of making yet another code switch and eventually returning to Rugby Union.
"If things work out I'd like to one day come back," he said, adding: "But I'm not going to hold my breath because there are good players coming up.
“I didn't think I would have loved it as much as I have back here. To be honest, I kind of felt like I'd found my place at the Chiefs, with the boys, but it just goes back to [the fact] I've given someone my word, this was a while ago, and I've had to go on with it even though it was tough."
The 26-year-old says at the time he made the commitment to League he was not confident he could return to New Zealand and make a success in the Union code.
“I might not have been good enough and pressure was certainly on me, it wasn't on anyone else.
“If it was about the money then I would have just stayed in France [with Toulon] where I was getting pretty good coin.”
The new All Black coach, Hansen, likened Williams to another famous Kiwi convert ... now retired Brad Thorn.
"He came to New Zealand rugby two years ago as a 'convert' player and was similar to Brad Thorn in that regard - players with high-level skills and freakish abilities without a fully developed game understanding for the new code.
"This season we have seen the birth of Sonny as a rugby [Union] player, with his game understanding now complementing his array of skills. His performances in the Tests against Ireland reflected this - he was world class.
"It is a shame and disappointing that New Zealand rugby is losing him. In talking to him, I know the decision has been a tough one but we fully respect why he has made this decision. He is an outstanding athlete who has stamped his mark on the game and hopefully this is not the last time we see him in New Zealand rugby.
"I would also like to acknowledge Sonny's manager Koder Nasser. Koder has been nothing but straight up in his dealings with myself and the NZRU and kept us informed right from day one. We may not always agree, but we have appreciated his honesty and transparency."
Chiefs Coach Dave Rennie said: "Sonny has been an important part of the Chiefs family this year. His professionalism, attitude and commitment have been a real asset to our environment.
"We appreciate everything he has done for our franchise. His Chiefs family completely understand and respect his decision and will watch and support his future endeavours closely. He will always be welcome back."
NZRU CEO Steve Tew said Williams had exercised a right under his contract to leave New Zealand rugby following the Super Rugby competition and also noted that Williams had advised that he would not be seeking to return to New Zealand rugby in 2013, but has not ruled out a return to New Zealand rugby in the future.
"We want to wish Sonny all the very best and thank him for the contribution he has made to New Zealand rugby."
Sonny Bill Williams has played 17 Tests for the All Blacks and more than 20 Super Rugby matches for the Chiefs and Crusaders and joined New Zealand rugby in 2010, first playing for Canterbury in the NPC.
With his size, strength and trademark off-loads he made an immediate impact, became a fan favourite, and was picked for the All Blacks on the 2010 end of year tour, playing in four Tests.
He played for the Crusaders in the 2011 Super Rugby season and his impressive form saw him selected again for the All Blacks Tri-Nations side and World Cup-winning squad.
He made the switch to the Chiefs in 2012 and his outstanding play saw him again selected for the All Blacks against Ireland and he scored two tries in the team's 60-0 third Test win.
rugby365 & AFP