As it stands, players must be plying their trade in New Zealand to be considered for the All Blacks but with a collection of young players - Charles Piutau, Colin Slade and Tom Taylor - announcing moves to Europe, calls have come for NZR to have a rethink.
"We can never say never," Tew said with regards to a policy change. "Policies need to be reviewed on a regular cycle and that will be the case but right now there is no indication we would be looking to change that.
"Right now, our policy has held us in good stead and we will continue it."
Hypothetically speaking, Tew said there were issues around picking European-based players such as the crossover of seasons with the Southern Hemisphere and gauging a player's form against Super Rugby players.
Tew said NZR tried their best to create contracts that catered to individuals and offered them things that were relevant to them.
"We've been really flexible in that regard."
Tew also pointed to the fact that many players had remained in New Zealand during the past decade, which had contributed to a string of good results for the All Blacks, including a World Cup triumph in 2011.
"We've had a strong run of player retention over two World Cup cycles."
The money on offer in Europe would remain tempting for players but Tew believed the lure of the black jersey would continue to keep players on these shores.
"We are not panicking but we are under pressure," Tew said. "But we have been for a long period of time."
Tew was speaking during a break at the NZR's annual meeting in Wellington today where the organisation confirmed a $373,000 profit for the year.
NZR grades itself internally and they achieved 79/100 based on their performance indicators but one area of concern was around how many teenagers were playing the game, particularly in Auckland, which is fertile ground for future talent.
"We've clearly got an issue with teenagers across the country actually," Tew said. "Our teenage drop off, like for a lot of sport, particularly organised team sport, is very severe."
Tew said everything remained on track for the All Blacks' historic test match against Samoa in Apia in July.