So'oialo, 30, was told he wasn't required for the All Blacks' June tests and with his Hurricanes teammate, winger David Smith, has accepted invitations to join the Barbarians squad for their matches against England at Twickenham on May 30 and Ireland at Limerick on June 4.
All Blacks coach Graham Henry said So'oialo, with 62 tests to his name, departed for England with the support of the selectors but didn't rule out a return to test rugby.
"We have the utmost respect for Rodney and his commitment to the black jersey and he goes with our blessing. However, it's important to note that he is by no means out of our thinking when it comes to future selection," Henry said.
So'oialo slipped down the All Blacks' pecking order last year as Kieran Read established himself as the first choice No 8. So'oialo captained the second-string All Blacks to victory against Italy in Milan last November.
So'oialo said the Barbarians matches would give him the chance to keep his form and match fitness up.
"I'm looking forward to playing the two games against some quality opposition. I know what I need to do to work on my game and will continue to push for All Blacks selection," he said in a statement.
"I am very honoured to receive this invitation and appreciate the temporary release from the New Zealand Rugby Union (NZRU) to enable me to accept it. Playing for or against the Baabaas is part of the special tradition of the international game and all players and rugby nations value that special opportunity."
