Steven Shingler remains tied to Wales and ineligible for Scotland - barring an unlikely set of circumstances - following today's International Rugby Board ruling on his case.

The Swansea-born fly-half or centre was included in Scotland head coach Andy Robinson's provisional squad for the RBS 6 Nations, sparking an investigation into his eligibility.

The Scottish Rugby Union believed the 20-year-old London Irish player qualified through his Dumfries-born mother, but the Welsh Rugby Union contended Shingler was tied to them having played for their Under-20s side against France in 2011, despite having not signed a declaration to that effect.

Today it was ruled Shingler is eligible only for Wales but the eligibility criteria could be overhauled by the IRB council in May, excluding under-20 teams from being a capturing team.

The IRB council can overturn decisions by the regulations committee and though any new law would not be applied retroactively, Shingler's case arose during the review on eligibility launched in April 2011 - meaning it is feasible, though unlikely, they could reopen the door for him to represent Scotland.

The SRU have decided to bide their time and await full written judgement of the ruling before deciding how to proceed over Shingler, whose brother Aaron made his Wales debut at flanker against Scotland last month.

Responding to the IRB's announcement, the SRU issued a statement, which read: "We remain fully supportive of Steven Shingler, a talented young rugby player who has expressed his sincere and earnest wish to represent Scotland.

"We await the full written decision of the IRB regulations committee and may comment further on receipt."

Neither Wales nor France field an A team and the WRU challenged the SRU's initial assertion in January that Shingler was eligible for Scotland, citing IRB regulation eight on international eligibility.

The SRU responded, citing the complex cases of Matthew Jarvis and James Loxton, who played for Wales Under-20s in 2010, a year prior to Shingler, before switching allegiance to Ireland.

The cases of Jarvis and Loxton prompted the global review, which recommended playing for an under-20 team should no longer commit that player to that nation.

The two issues are separate, yet interlinked. If the IRB council ratify the recommendations and due to the timing of the Shingler case, they may apply the new law to him specifically.

However, that appears unlikely as the IRB made specific reference to the review in announcing their decision over Shingler today.

Today's ruling came as little surprise as an initial informal assessment by the IRB determined that the player appeared to be tied to Wales. That prompted the SRU to formally request the IRB regulations committee review the case, with a three-man regulations committee panel chaired by Peter Boyle (Ireland) and also comprising Giancarlo Dondi (Italy) and Tim Gresson (New Zealand) hearing evidence from Shingler, his agent and the Scottish and Welsh Rugby Unions at a hearing in Dublin on February 27.

In announcing their verdict, a statement from the IRB read: "The IRB regulations committee panel hearing the Steven Shingler eligibility case has determined that the player is tied to Wales in accordance with IRB regulation eight as it stands and therefore is ineligible to represent another Union.

"This decision is binding on the parties until it is endorsed or overturned by the IRB council.

"The panel noted that, in accordance with IRB regulation eight, playing in a designated capturing match (Wales Under-20s' match with France) was the key determining factor with regard to the player's eligibility."

The panel acknowledged in their judgement the recommendation of the potential scrapping of the under-20s as the next senior side, and that the timing could impact on Shingler's case.

The IRB statement added: "The panel further recognised that the IRB council will have made its determination on the recommendations of both committees regarding the next senior national representative team review prior to its consideration of the regulations committee decision in the Shingler case.

"Council, in accordance with IRB regulation two, is able to endorse or overturn the decision of the regulations committee.

"It should also be noted that unless specifically stated by council, changes to laws and regulations do not have retrospective application."