Jamie Roberts may not be fully available to Wales after joining Harlequins.
The same would apply to Newport Gwent Dragon Taulupe Faletau if he joins Bath after the 2015 World Cup.
Coach Warren Gatland recently stated Faletau, like Roberts, would be free for all Wales duties.
However, an Aviva Premiership spokesman said: "Our policy hasn't changed. We release players under the confines of World Rugby regulation nine."
That regulation stipulates teams are not obliged to free players for Test and training duty outside designated international match windows.
Wales regularly play at least one autumn Test outside that calendar slot.
At a press conference on 25 June, Gatland was asked if Faletau would be free for all Wales commitments if he joins Bath.
The New Zealander replied: "That's an important factor, isn't it? My understanding is that he'd get the same as Jamie Roberts."
After Roberts' joining Harlequins was confirmed, boss Connor O'Shea said the British and Irish Lions centre would be available for Wales "whenever he needs to be".
That now appears to contradict the official statement from the umbrella body representing England's leading clubs.
Reports have suggested Faletau's proposed move to Bath could be halted amid uncertainty over his full availability for Wales.
Gatland could veto any plan by Dragons to release him before his contract expires in the summer of 2016 under an agreement between the Welsh Rugby Union and the nation's four regions.
The Premiership clubs' stance led to Northampton being fined £60,000 for signing George North on the basis he was available for all Wales commitments.
He joined Northampton in April 2013 and played for Wales against Australia the following November.
Since then Wales fly-half Rhys Priestland has committed his post-World Cup future to Bath.
Priestland has admitted his Test prospects could be damaged by moving there from Scarlets.