Newport Gwent Dragons have to allow Taulupe Faletau to leave, says former Wales forward Jonathan Thomas.
The region have asked the Welsh Rugby Union for permission to transfer the 24-year-old number eight.
Faletau has a year left on his current deal and Wales head coach Warren Gatland would need to approve the move.
"You presume he doesn't want to be at the Dragons, and if you're a player and you don't want to be there then you've simply got to go," said Thomas.
"The fact that they [Dragons] have written to the WRU then it seems they have to let him go, because if he doesn't then he'll go in the summer and that will be a £150,000 fee gone for the Dragons.
"I'm sure the Dragons have explored every single option over the past 12 months to try and keep him, but the fact that he hasn't re-signed [a new contract] shows that he doesn't want to be there and I don't see what the debate is really."
Bath probable destination
Bath are favourites to sign the 52-times capped Faletau, with the Dragons board expecting a six-figure fee.
But Gatland has previously said he would not sanction such a transfer as it would potentially make Faletau unavailable for the national side.
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The professional game in Wales is run under the Rugby Services Agreement (RSA) - a legally-binding contract between the Union and the four regions.
Under the RSA, Gatland can select only two players who have moved to play outside Wales since the agreement came into force in August.
Centre Jamie Roberts and fly-half Rhys Priestland, who have joined Harlequins and Bath respectively, would come under its jurisdiction.
England better than France
But Thomas, who finished his playing career with Worcester, says Faletau moving to England was preferable to a transfer into French rugby.
"For me, players going to France is a much bigger problem," he said.
"Being 45 minutes down the road... is not the end of the world.
"I've experienced playing in England for 12 months and I think it will be good for him in terms of rugby experience.
"He'll play with great players, he'll see things from a different perspective and I think it will enhance him."