Having slipped behind Scarlets' playmaker Rhys Priestland in the fly-half pecking order at the recent World Cup, the news that his new employers will require him for domestic action when his Wales colleagues are in camp on the last weekend of January will be a bitter blow to Hook's hopes of regaining his spot in Warren Gatland's starting XV.
"James will stay with Perpignan because our game against Brive is too important," Perpignan president Paul Goze told Wales Online when asked if Hook would be allowed to join the training a fortnight before the start of the tournament on February 5.
"We will release him for the Six Nations tournament but, if Mr Gatland needs him earlier, the answer at this moment would have to be no."
Fellow Lion Mike Phillips looks set to face similar difficulties following his move to Bayonne, while full back Lee Byrne's new club Clermont Auvergne have yet to comment on his availability.
"For me, it's a big problem," was the blunt assessment of Bayonne's caretaker coach Jean-Pierre Elissalde.
Gatland has previously claimed that players unavailable for the entire training camp wouldn't be selected for his 6 Nations squad, although that stance will surely now be tested if the likes of Hook, Phillips and Byrne fall all into that category.
"If those players in France, along with English players, can't get full release for the Six Nations they will not be selected in the squad," was Gatland's public stance, although did make it clear that distinctions would need to be made between those who left because of a lack of interest from Welsh regions and those who moved on for financial reasons.
"There have been one or two who have left Wales because they haven't been wanted by the other regions. That's something we have to be mindful of."