In a letter to the Welsh Region the Union says it wants the Dragons to fulfil the contractual agreement which ensures the player remains with them at least until the end of season 2015/16.
The letter from Wales Head Coach, Warren Gatland, explains the decision is based on the commitment in the Rugby Services Agreement between the WRU and the Welsh Regions to limit the number of players being selected from outside Wales in future.
The decision to reject the Newport Gwent Dragons’ request to release the contracted player was taken after full consultation between the coach and the Group Chief Executive of the WRU, Martyn Phillips.
Martyn Phillips said: “We stand alongside the Regions in our commitment to try to keep the best Welsh qualified players here in Wales where they can compete for international honours.
“We want the best players in Wales as role models for youngsters, making sure the Regions are as competitive as possible and making sure the coaches are working with the finest talent.
“It is important that supporters recognise our commitment here as we know they want to be watching the very best talent and we want these fans to turn up at Regional games as there’s nothing better for our players than to be performing in front of big crowds.
“We fully understand that the Newport Gwent Dragons have acted entirely properly in this matter, but we have a duty to act in the way we feel is in the best interests of the whole of professional rugby and the international game in Wales.
“Although there are circumstances under which moves out of Wales by experienced players can be sanctioned, Taulupe’s status as a player and importance as a role model means we would like him to be playing his rugby here.
“Clearly it is vitally important that we are all mindful of the need to respect and protect Taulupe himself throughout this extremely sensitive and delicate discussion. His welfare is paramount.
“Taulupe is under contract until the end of the current season and we do not believe it is in any of our interests to withdraw from that agreement.
“He is a 24-year-old with a lot more to offer Wales and our desire now is to keep him under the umbrella of our systems and structures to ensure he has the best opportunity to achieve his full potential.
“I want Taulupe to know we have his and the interests of all our players at the heart of all our decision making.”
Taulupe Faletau has won 52 caps for Wales.