The 23-year-old has been caught up in a legal battle, as current club Castleford - to whom he is contracted for another two years - are unhappy with the way he has gone about his business.
Solomona has been registered to play for Sale, a month after his supposed retirement from rugby league, but Rugby Football League chief Nigel Wood admitted earlier this week that he was concerned about the possible negative implications the move would bring.
The RFU says that it respects these concerns, but are powerless to prevent any transfer going through.
"The employment status with a club in a different sport is a matter between that club and the player," a spokesman told BBC Sport.
Solomona set a Super League try-scoring record this year by crossing over 40 times for Cas.