Most recent high profile example of this comes in Freddie Kanoute's decision to represent Mail at the African Nations, despite Under 21 honours for his native France.
Hughes did welcome Thatcher's change of allegiance, a move which is likely to see Barnard lose his starting place.
"Ben is committed to this new change in his career," the former overhead kick king said.
"His agent contacted me to make me aware of his qualification, and I am delighted to have him on board, we need as many Premiership players as possible.
"I have no problems with what people call a tradesman's entry to our squad.
"I have played with the likes of John Robinson and Eric Young - neither of whom were Welsh - but you could not have found more committed players."
Former Mariners Danny Coyne and John Oster are again in the squad.Full squad to face Scotland at the Millenium Stadium on February 18:
Coyne (Leicester), Jones (Wolves), Ward (Nottm For), Crossley (Fulham); Melville (Fulham), Pembridge (Fulham), Delaney, (Aston Villa), Edwards (Aston Villa), Gabbidon (Cardiff), Page (Sheff Utd), Thatcher (Leicester), Williams (Reading), Barnard (Grimsby); Davies (Tottenham), Giggs (Man Utd), Johnson (West Brom), Koumas (West Brom), Oster (Sunderland), Robinson (Portsmouth), Savage (Birmingham), Speed (Newcastle); Bellamy (Newcastle), Blake (Wolves), Hartson (Celtic), Taylor (Nottm For), Earnshaw (Cardiff).