The International Rugby Board said Friday they would review the eligibility of Steven Shingler after a row between Scotland and Wales over the Swansea-born player's decision to play for Scotland.
Shingler, 20, was named in Scotland's Six Nations squad on Thursday despite having played Welsh international junior rugby.
Scotland coach Andy Robinson picked the London Irish fly-half/centre on the grounds that he has a mother born in Scotland.
However Wales Rugby Union officials later pointed out that Shingler had already played for Wales Under-20s last year and was therefore tied to Welsh rugby at international level.
With the two unions unable to find agreement, the IRB has confirmed it will review the case.
"The International Rugby Board can confirm that it has been contacted by the Scottish Rugby Union and Welsh Rugby Union regarding the eligibility status of Steven Shingler," the board said.
"It would be inappropriate to make any further comment until the matter has been fully reviewed and the Unions informed of the outcome."