Scotland coach Andy Robinson named the 20-year-old in his 36-man squad for the RBS 6 Nations openers against England at Murrayfield and Wales in Cardiff, believing Shingler to be available for selection through his mother, who hails from Langholm.
The London Irish centre or fly-half was born in Swansea, and the WRU has contended that he is not eligible to play for another nation after playing full-back for Wales Under-20s against their French counterparts last year. That outing would appear to tie him to Wales under the terms of IRB Regulation Eight, as both sides were nominated as their respective unions’ second senior sides, meaning players involved in that fixture are effectively committed to their nations.
But Scotland say that Shingler, who also played for Wales Under-20s at last summer’s Junior World Championship in Italy, assured them that he kept his eligibility open by refusing to sign a declaration committing himself to Wales.
The world governing body has now confirmed it will look into the matter after being contacted by the WRU and the SRU.
The SRU released a statement on Thursday that said: “Steven has confirmed to Scottish Rugby that he declined to sign a declaration from the WRU that he was committed solely to representing Wales at senior level. Steven has informed us that he made it clear that he wished to leave open his international eligibility as he was also eligible to represent Scotland and England as well as Wales.
“Scottish Rugby believes we have acted in good faith in this matter and have also taken cognisance of an IRB ruling last year concerning two players who played for Wales Under-20 against France Under-20 in 2010 who now play for Connacht and are eligible for Ireland.”
The SRU were referring to a ruling relating to former Wales Under-20 internationals Matthew Jarvis and James Loxton, in which a precedent may have been set allowing Shingler to play for Scotland. The pair, who joined Connacht last year, can play for Ireland despite playing at under-20 level for Wales.